fix(installer): wrap shortcut Target in 'runas /trustlevel:0x20000'

The in-process ShouldDeElevate check (commit 191b2c5) didn't fire on the test box because ParticipantPID resolution against Win32_Process can return null fast enough that the check skips before the elevated explorer-spawned TeamsISO has fully booted. Belt-and-braces: ALSO wrap the shortcut Target so the runas demotion happens at shell-launch time, before TeamsISO.exe even runs. Result on the dev box: clicking the Start Menu / Desktop shortcut now lands a working medium-integrity TeamsISO with NDI discovery succeeding, regardless of explorer's elevation.

Uses [SystemFolder]runas.exe (resolved by MSI at install time) and Show='minimized' to hide the brief runas console flash.

installer/Package.wxs

@@ -113,17 +113,39 @@
     </ComponentGroup>
 
     <!--
-        Start Menu shortcut to the WPF host. KeyPath sits on a per-user
-        registry value because the .lnk file lives in a per-user Start Menu
-        folder (ICE38/ICE43 enforce this even for perMachine installs).
+        Start Menu and Desktop shortcuts. The Target is intentionally
+        runas.exe (NOT TeamsISO.exe directly) with the /trustlevel:0x20000
+        argument. This drops the spawned TeamsISO to MEDIUM integrity even
+        when the shortcut is invoked from an elevated File Explorer.
+
+        Why: on admin-user boxes with UAC effectively disabled, double-
+        clicking the .lnk has explorer.exe as the spawner — and when the
+        spawned TeamsISO inherits explorer's elevated token, NDI Find
+        returns zero discovered sources (suspected window-station / desktop
+        handle inheritance quirk in NDI's mDNS layer; not reproducible from
+        any other parent). Wrapping with /trustlevel:0x20000 forces the
+        child to a restricted medium-integrity token regardless of the
+        invoking shell's level. Empirically verified to make discovery
+        succeed on the dev box where the bug first surfaced.
+
+        The /trustlevel:0x20000 magic number is the Windows "Basic User"
+        SAFER trust level — documented at
+        https://learn.microsoft.com/windows/security/identity-protection/windows-credential-theft-mitigation-guide-appendix#runas
+
+        Icon points at TeamsISO.exe (not runas) so the shortcut still shows
+        the app's icon, and WindowStyle=Minimized hides the brief runas
+        console flash.
     -->
     <ComponentGroup Id="Shortcuts" Directory="WildDragonStartMenuFolder">
       <Component Id="StartMenuShortcut" Guid="*">
         <Shortcut Id="StartMenuTeamsISO"
                   Name="TeamsISO"
                   Description="Per-Participant NDI ISO Controller for Microsoft Teams"
-                  Target="[INSTALLFOLDER]TeamsISO.exe"
-                  WorkingDirectory="INSTALLFOLDER" />
+                  Target="[SystemFolder]runas.exe"
+                  Arguments="/trustlevel:0x20000 &quot;[INSTALLFOLDER]TeamsISO.exe&quot;"
+                  WorkingDirectory="INSTALLFOLDER"
+                  Icon="TeamsISOIcon"
+                  Show="minimized" />
         <!-- Required by ICE64: Start Menu folder must be cleaned on uninstall. -->
         <RemoveFolder Id="RemoveWildDragonStartMenuFolder"
                       Directory="WildDragonStartMenuFolder"
@@ -137,20 +159,17 @@
       </Component>
     </ComponentGroup>
 
-    <!--
-        Desktop shortcut — belt-and-braces. Operators who lose the Start Menu
-        entry (or whose Start Menu doesn't materialize advertised shortcuts
-        cleanly) still get a Desktop icon. Same HKCU keypath rule as above.
-    -->
     <StandardDirectory Id="DesktopFolder" />
     <ComponentGroup Id="DesktopShortcut" Directory="DesktopFolder">
       <Component Id="DesktopShortcutComponent" Guid="*">
         <Shortcut Id="DesktopTeamsISO"
                   Name="TeamsISO"
                   Description="Per-Participant NDI ISO Controller for Microsoft Teams"
-                  Target="[INSTALLFOLDER]TeamsISO.exe"
+                  Target="[SystemFolder]runas.exe"
+                  Arguments="/trustlevel:0x20000 &quot;[INSTALLFOLDER]TeamsISO.exe&quot;"
                   WorkingDirectory="INSTALLFOLDER"
-                  Icon="TeamsISOIcon" />
+                  Icon="TeamsISOIcon"
+                  Show="minimized" />
         <RegistryValue Root="HKCU"
                        Key="Software\Wild Dragon\TeamsISO"
                        Name="DesktopShortcut"