Four polish improvements aimed at production-floor usability.
1. Empty-state placeholder for the participants card. When Participants.Count == 0, the DataGrid is hidden in favor of a friendly 'Waiting for Teams' panel: faded dragon mark, headline, explainer, and a four-item checklist (Teams running? NDI broadcast on? Discovery group correct? Firewall clear?). New CountToVisibilityConverter (with optional 'empty' parameter to invert) drives both the placeholder and the DataGrid visibility from the same Participants.Count source.
2. Per-pipeline error / no-signal surfacing. IsoHealthStats grows an init-only State property populated from IsoPipeline.State. ParticipantViewModel.UpdateStats maps that to a StateLabel ('LIVE' / 'NO SIGNAL' / 'ERROR' / 'STARTING' / '—'). The ISO toggle button gains DataTriggers on StateLabel — coral-tinted '● ERROR' when the supervisor gives up, amber-tinted '● NO SIGNAL' when the slate threshold trips. Operators can see at a glance which pipelines are broken.
3. JetBrains Mono Variable v2.304 (OFL) bundled at Assets/Fonts/JetBrainsMono.ttf. Wd.Font.Mono now points at the embedded font so machine names, timecodes, and stat counters render in JetBrains Mono regardless of system fonts. Falls back to Cascadia Mono / Consolas if the resource is missing.
4. Tooltip pass over every interactive control in the settings panel (framerate / resolution / aspect / audio / discovery group / output group / hide-local checkbox / Apply button / per-row Output Name textbox / per-row ISO toggle). Operators learn affordances on hover instead of by trial and error.
Tests: 76/76 unit + 9/9 NDI integration green.
Four polish items + a test pass.
1. Inter Variable (rsms/inter v3.19, OFL) is bundled at Assets/Fonts/Inter.ttf (~800 KB) and registered as a WPF Resource. WildDragonTheme.xaml's Wd.Font.Sans now points at pack://application:,,,/Assets/Fonts/#Inter so the typography matches wilddragon.net regardless of whether the user has Inter installed system-wide. Falls back to Segoe UI Variable Display if the resource is missing.
2. 'Stop all ISOs' button at the right of the participants header. Bound to a new MainViewModel.StopAllIsosCommand that snapshots the enabled list, awaits DisableIsoAsync sequentially, and silently swallows per-pipeline failures (best-effort emergency stop). CanExecute gates on whether any ISO is currently enabled.
3. WindowStateStore service persists the main window's Left/Top/Width/Height/State to %LOCALAPPDATA%\\TeamsISO\\window.json on close and restores it on SourceInitialized. Multi-monitor friendly: a saved position with no corner inside any virtual screen is rejected so a disconnected monitor doesn't strand the window off-screen.
4. Two new unit tests cover FrameProcessor's drops + duplicates accounting. 76/76 unit tests pass (was 74).
