polish(mainwindow): empty state, table widths, strings, theme tooltip

Walks the v2 polish punch list against MainWindow.

- Theme button tooltip is now "Theme (System / Dark / Light)" per the
  v2 shape brief, replacing the previous "Toggle theme (Ctrl+T)".
- Participants table column widths match spec: Output 130px (was 150),
  ISO pill 100px (was 110). The 24px state LED, 110px audio meter, and
  52px row height already matched. The 106px Preview thumbnail column
  and 32px gear-button column are intentional deviations (live thumbs
  were restored at 4944de5; per-ISO override gear added at the same
  time) and are now called out in the column-spec comment so a future
  reader doesn't try to "fix" them.
- Empty-state placeholder finally renders when ParticipantCount == 0:
  mono sentence "no ndi sources yet — open teams and start a meeting"
  + a tertiary Refresh discovery button — exactly the copy specified
  by the shape brief's empty-states section. CountToVisibilityConverter
  is now declared in MainWindow.Resources (it shipped as a class but
  was never registered).
- OnClosing wraps WindowStateStore.Save in a try/catch so a serialization
  or filesystem fault on shutdown can never block the window from
  closing. Save itself already swallows its own IO errors; this is
  defense-in-depth for anything that escapes.
- MessageBox copy in MainWindow.xaml.cs (Hide/show Teams, Launch Teams,
  Stop Teams) moves to Properties/Strings.resx + a hand-written
  Properties/Strings.Designer.cs accessor. ResourceManager reads it by
  basename "TeamsISO.App.Properties.Strings"; LogicalName is set on the
  EmbeddedResource so the manifest name is predictable regardless of
  how MSBuild would otherwise compute it. Future-localization seam.
  OnLaunchTeamsRightClick's confirmation dialog is intentional — it
  guards a destructive mid-show action — and the code-behind comment
  now says so; the palette also offers Stop Teams as the keyboard
  surface, so the right-click affordance isn't the only one.

Build clean (0 warnings, 0 errors); 160 tests still pass (56 App +
104 Engine, Category!=ndi&requires!=ndi filter).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/TeamsISO.App/MainWindow.xaml

@@ -39,6 +39,7 @@
                                         FalseValue="Visible"/>
         <conv:EnumDescriptionConverter x:Key="EnumDesc"/>
         <conv:LevelThresholdConverter x:Key="LevelGate"/>
+        <conv:CountToVisibilityConverter x:Key="CountToVis"/>
     </Window.Resources>
 
     <Window.InputBindings>
@@ -138,7 +139,7 @@
                             Command="{Binding ToggleThemeCommand}"
                             Padding="6,4"
                             Margin="0,0,2,0"
-                            ToolTip="Toggle theme (Ctrl+T)">
+                            ToolTip="Theme (System / Dark / Light)">
                         <Path Data="M 8,2 C 8,2 4,4 4,8 C 4,12 8,14 8,14 C 5,14 2,11 2,8 C 2,5 5,2 8,2 Z"
                               Stroke="{DynamicResource Wd.Text.Secondary}"
                               StrokeThickness="1.4"
@@ -410,7 +411,7 @@
             <!--
                 Participants table — v2 "Studio Terminal" layout.
 
-                Five columns:
+                Spec columns (from docs/shapes/2026-05-13-…studio-terminal.md):
                   1. State LED        24px  — 8×8 hard-edged square. Filled cyan
                                               when LIVE; filled coral on ERROR;
                                               filled amber on NO SIGNAL / STARTING;
@@ -422,12 +423,22 @@
                                               each lit when DisplayedAudioLevel
                                               crosses its threshold (0.2, 0.4,
                                               0.6, 0.8, 1.0). No averaging.
-                  4. Output name      150px — JetBrains Mono 12 — the NDI source
+                  4. Output name      130px — JetBrains Mono 12 — the NDI source
                                               name TeamsISO broadcasts as.
-                  5. ISO toggle pill  110px — LIVE = cyan-muted fill with cyan
+                  5. ISO toggle pill  100px — LIVE = cyan-muted fill with cyan
                                               text; OFF = hollow neutral; ERROR
                                               gets the existing trigger swap.
 
+                Deliberate deviations from the spec (operator preference, see
+                4944de5 — "restore live thumbnail preview column"):
+                  • A 106px live thumbnail column sits between State LED and
+                    Name. Replaces the table's previous role as the only place
+                    to see what the operator is broadcasting; the pop-out
+                    preview window is the secondary view.
+                  • A 32px ghost-button cell on the right edge of Name opens
+                    the per-ISO override dialog (framerate / resolution /
+                    aspect / audio). Hidden on hover-out.
+
                 Row height 52 (down from 56). Active speaker = full-row
                 bg.active-speaker tint set by the global DataGridRow style
                 (avoids the impeccable side-stripe-border ban).
@@ -438,6 +449,7 @@
                     BorderThickness="1"
                     CornerRadius="{StaticResource Radius.M}"
                     Background="{DynamicResource Wd.Surface}">
+                <Grid>
                 <DataGrid x:Name="ParticipantsGrid"
                           ItemsSource="{Binding ParticipantsView}"
                           AutoGenerateColumns="False"
@@ -451,7 +463,8 @@
                           CanUserResizeRows="False"
                           SelectionMode="Single"
                           SelectionUnit="FullRow"
-                          RowHeight="52">
+                          RowHeight="52"
+                          Visibility="{Binding ParticipantCount, Converter={StaticResource CountToVis}}">
                     <DataGrid.Columns>
                         <!-- Col 1 — State LED. 8×8 hard-edged Rectangle.
                              Default fill is hollow (transparent with stroke). DataTriggers
@@ -601,7 +614,7 @@
 
                         <!-- Col 4 — Output name (mono). The NDI source name TeamsISO
                              will broadcast this participant as. -->
-                        <DataGridTemplateColumn Header="Output" Width="150" IsReadOnly="True">
+                        <DataGridTemplateColumn Header="Output" Width="130" IsReadOnly="True">
                             <DataGridTemplateColumn.CellTemplate>
                                 <DataTemplate>
                                     <TextBlock Text="{Binding OutputName}"
@@ -639,7 +652,7 @@
 
                         <!-- Col 5 — ISO toggle pill. LIVE = cyan-muted fill + cyan border + cyan text.
                              OFF = hollow neutral. Error states use the existing IsoToggle style. -->
-                        <DataGridTemplateColumn Header="ISO" Width="110">
+                        <DataGridTemplateColumn Header="ISO" Width="100">
                             <DataGridTemplateColumn.CellTemplate>
                                 <DataTemplate>
                                     <Button Command="{Binding ToggleIsoCommand}"
@@ -665,6 +678,30 @@
                         </DataGridTemplateColumn>
                     </DataGrid.Columns>
                 </DataGrid>
+
+                <!-- Empty-state placeholder. Renders when no NDI participants
+                     have been discovered yet. Mono sentence + one tertiary
+                     Refresh button — no illustration, no mascot, per the v2
+                     shape brief's empty-states section. -->
+                <StackPanel HorizontalAlignment="Center"
+                            VerticalAlignment="Center"
+                            Visibility="{Binding ParticipantCount, Converter={StaticResource CountToVis}, ConverterParameter=empty}">
+                    <TextBlock Text="no ndi sources yet — open teams and start a meeting"
+                               FontFamily="{StaticResource Wd.Font.Mono}"
+                               FontSize="12"
+                               Foreground="{DynamicResource Wd.Text.Tertiary}"
+                               HorizontalAlignment="Center"/>
+                    <Button Style="{StaticResource Wd.Button.Ghost}"
+                            Command="{Binding RefreshDiscoveryCommand}"
+                            Content="Refresh discovery (Ctrl+R)"
+                            Padding="14,7"
+                            Margin="0,14,0,0"
+                            HorizontalAlignment="Center"
+                            FontFamily="{StaticResource Wd.Font.Mono}"
+                            FontSize="11"
+                            ToolTip="Rebuild the NDI finder"/>
+                </StackPanel>
+                </Grid>
             </Border>
         </Grid>
 

src/TeamsISO.App/MainWindow.xaml.cs

@@ -42,7 +42,12 @@ public partial class MainWindow : Window
     /// <summary>Persist the placement on close so next launch lands in the same spot.</summary>
     private void OnClosing(object? sender, System.ComponentModel.CancelEventArgs e)
     {
-        WindowStateStore.Save(this);
+        // A failure persisting window state must NEVER block the window from
+        // closing — operator's shutdown comes first. WindowStateStore.Save
+        // already swallows its own IO errors; this is defense-in-depth for
+        // anything that escapes (NRE, future regression, etc.).
+        try { WindowStateStore.Save(this); }
+        catch { /* best-effort: forgo placement memory for one launch */ }
     }
 
     /// <summary>Opens the About dialog — version, NDI runtime, build SHA.</summary>
@@ -87,8 +92,8 @@ public partial class MainWindow : Window
         if (!TeamsLauncher.IsRunning())
         {
             MessageBox.Show(
-                "Microsoft Teams isn't running. Click the camera icon above to launch it first.",
+                Properties.Strings.HideShowTeams_NotRunning_Message,
-                "TeamsISO — Hide / show Teams",
+                Properties.Strings.HideShowTeams_Title,
                 MessageBoxButton.OK,
                 MessageBoxImage.Information);
             return;
@@ -125,8 +130,8 @@ public partial class MainWindow : Window
             if (!TeamsLauncher.TryLaunch(out var error))
             {
                 MessageBox.Show(
-                    $"Could not launch Microsoft Teams.\n\n{error}",
+                    string.Format(Properties.Strings.LaunchTeams_Failed_MessageFormat, error),
-                    "TeamsISO — Launch Teams",
+                    Properties.Strings.LaunchTeams_Title,
                     MessageBoxButton.OK,
                     MessageBoxImage.Warning);
             }
@@ -159,15 +164,19 @@ public partial class MainWindow : Window
     /// <summary>
     /// Right-click on the Launch button asks to stop Teams. Split out from the
     /// left-click so a normal click is "open / surface" rather than the previous
-    /// "open OR ambush you with a stop dialog".
+    /// "open OR ambush you with a stop dialog". The confirmation dialog here is
+    /// intentional — Stop Teams is a destructive mid-show action; explicit
+    /// confirmation is the right pattern, not the "ambush" anti-pattern that
+    /// was fixed for left-click. The palette also offers Stop Teams for
+    /// keyboard-first operators.
     /// </summary>
     private void OnLaunchTeamsRightClick(object sender, MouseButtonEventArgs e)
     {
         if (!TeamsLauncher.IsRunning()) return;
 
         var confirm = MessageBox.Show(
-            "Microsoft Teams is currently running.\n\nClose all Teams windows now?",
+            Properties.Strings.StopTeams_Confirm_Message,
-            "TeamsISO — Stop Teams",
+            Properties.Strings.StopTeams_Title,
             MessageBoxButton.YesNo,
             MessageBoxImage.Question);
         if (confirm != MessageBoxResult.Yes) return;
@@ -177,9 +186,9 @@ public partial class MainWindow : Window
         {
             MessageBox.Show(
                 asked == 0
-                    ? "No Teams windows responded to close."
+                    ? Properties.Strings.StopTeams_NoneResponded
-                    : $"Sent close to {asked} Teams window(s); some may still be exiting.",
+                    : string.Format(Properties.Strings.StopTeams_AskedFormat, asked),
-                "TeamsISO — Stop Teams",
+                Properties.Strings.StopTeams_Title,
                 MessageBoxButton.OK,
                 MessageBoxImage.Information);
         }

src/TeamsISO.App/Properties/Strings.Designer.cs

@@ -0,0 +1,36 @@
+// Hand-written strongly-typed accessor for Properties/Strings.resx. Kept
+// out of Visual Studio's "ResXFileCodeGenerator" auto-regeneration loop
+// so the .csproj stays simple and the file doesn't churn on every save.
+// If you add a key in Strings.resx, add a matching property here.
+
+// The compiler treats `*.Designer.cs` as auto-generated and refuses
+// nullable annotations without an explicit directive — opt in.
+#nullable enable
+
+using System.Globalization;
+using System.Resources;
+
+namespace TeamsISO.App.Properties;
+
+internal static class Strings
+{
+    private static readonly ResourceManager ResourceManager = new(
+        baseName: "TeamsISO.App.Properties.Strings",
+        assembly: typeof(Strings).Assembly);
+
+    public static CultureInfo? Culture { get; set; }
+
+    private static string Get(string key) =>
+        ResourceManager.GetString(key, Culture) ?? string.Empty;
+
+    public static string HideShowTeams_Title => Get(nameof(HideShowTeams_Title));
+    public static string HideShowTeams_NotRunning_Message => Get(nameof(HideShowTeams_NotRunning_Message));
+
+    public static string LaunchTeams_Title => Get(nameof(LaunchTeams_Title));
+    public static string LaunchTeams_Failed_MessageFormat => Get(nameof(LaunchTeams_Failed_MessageFormat));
+
+    public static string StopTeams_Title => Get(nameof(StopTeams_Title));
+    public static string StopTeams_Confirm_Message => Get(nameof(StopTeams_Confirm_Message));
+    public static string StopTeams_NoneResponded => Get(nameof(StopTeams_NoneResponded));
+    public static string StopTeams_AskedFormat => Get(nameof(StopTeams_AskedFormat));
+}

src/TeamsISO.App/Properties/Strings.resx

@@ -0,0 +1,75 @@
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!--
+    User-facing English strings shown by MainWindow's MessageBox prompts.
+    Pulled out of code-behind so a future localizer has a single seam to
+    translate. Strings.Designer.cs is a hand-rolled accessor backed by
+    ResourceManager — no Visual-Studio auto-regeneration needed.
+  -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype"><value>text/microsoft-resx</value></resheader>
+  <resheader name="version"><value>2.0</value></resheader>
+  <resheader name="reader"><value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value></resheader>
+  <resheader name="writer"><value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value></resheader>
+
+  <data name="HideShowTeams_Title" xml:space="preserve">
+    <value>TeamsISO — Hide / show Teams</value>
+  </data>
+  <data name="HideShowTeams_NotRunning_Message" xml:space="preserve">
+    <value>Microsoft Teams isn't running. Click the camera icon above to launch it first.</value>
+  </data>
+
+  <data name="LaunchTeams_Title" xml:space="preserve">
+    <value>TeamsISO — Launch Teams</value>
+  </data>
+  <data name="LaunchTeams_Failed_MessageFormat" xml:space="preserve">
+    <value>Could not launch Microsoft Teams.
+
+{0}</value>
+    <comment>{0} = error string from TeamsLauncher.TryLaunch.</comment>
+  </data>
+
+  <data name="StopTeams_Title" xml:space="preserve">
+    <value>TeamsISO — Stop Teams</value>
+  </data>
+  <data name="StopTeams_Confirm_Message" xml:space="preserve">
+    <value>Microsoft Teams is currently running.
+
+Close all Teams windows now?</value>
+  </data>
+  <data name="StopTeams_NoneResponded" xml:space="preserve">
+    <value>No Teams windows responded to close.</value>
+  </data>
+  <data name="StopTeams_AskedFormat" xml:space="preserve">
+    <value>Sent close to {0} Teams window(s); some may still be exiting.</value>
+    <comment>{0} = number of windows the launcher asked to close.</comment>
+  </data>
+</root>

src/TeamsISO.App/TeamsISO.App.csproj

@@ -39,6 +39,17 @@
     </AssemblyAttribute>
   </ItemGroup>
 
+  <!--
+    Strings.resx — user-facing English MessageBox copy. Embedded as a
+    .NET resource so ResourceManager can resolve TeamsISO.App.Properties.Strings
+    by basename. Strings.Designer.cs is hand-written (see file comment).
+  -->
+  <ItemGroup>
+    <EmbeddedResource Update="Properties\Strings.resx">
+      <LogicalName>TeamsISO.App.Properties.Strings.resources</LogicalName>
+    </EmbeddedResource>
+  </ItemGroup>
+
   <!-- Wild Dragon brand assets — embedded as resources so the published binary is self-contained. -->
   <ItemGroup>
     <Resource Include="Assets\dragon-mark.png" />