Code review on d14a33a..bab29b0 turned up three real issues, fixed here.
1. EngineLogging.CreateDefault no longer mutates Serilog.Log.Logger. The static set was a belt-and-suspenders attempt to catch any code path that reaches for the singleton, but it doesn't matter (engine code uses ILogger<T>, never Serilog.Log.*) and it raced under xUnit's parallel test execution.
2. IsoPipeline stops holding a RawFrame reference for stats. The receiver-side TappedChannelWriter callback now snapshots only Width/Height into volatile ints — frame's pixel buffer is allowed to GC on its normal schedule and a late stats poll can never resurrect a dropped frame. (Today the buffer is fully managed so a use-after-free wasn't actually possible, but the snapshot pattern is the right ownership shape.)
3. App.xaml.cs's ComponentDispatcher.ThreadFilterMessage subscription now lives in a field and is unsubscribed in OnExit. Mutex release is gated on a new _ownsSingleInstanceMutex flag so the 'lost the race; shut down silently' path doesn't accidentally try to release a handle it never owned.
Plus a load-bearing comment in NdiInteropPInvoke.CreateFinder explaining why we free the UTF-8 group buffers right after the native call returns — same lifetime contract Phase B-2's CreateReceiver / CreateSender have always relied on; if it's wrong, those would fail too. The loopback discovery integration test would catch a regression.
Tests: 74/74 unit + 9/9 NDI integration green.
Adds Serilog.Sinks.File to TeamsISO.Engine and a new EngineLogging.CreateDefault() factory that writes to BOTH the existing console sink and a rolling daily file at %LOCALAPPDATA%\\TeamsISO\\Logs\\teamsiso<date>.log. The WPF host (TeamsISO.exe is a WinExe with no console attached at runtime) now uses CreateDefault so support has something to ask for when users file an issue. The Console build keeps using CreateConsole — stdout is the right surface there and shell redirection beats a competing on-disk sink.
Files roll daily, cap at 10 MB before mid-day rollover, and only the most recent 14 are retained. Disk flush interval is 250 ms so a tail -f from another tool sees lines promptly. Path is announced via the first log line on every startup.
Two unit tests gate the wiring: AllLoggers_WriteToFile (verifies both typed and named CreateLogger() reach the file) and LogsAtBelowMinimumLevel_AreSuppressed (regression guard for level filtering). 74/74 unit tests pass (was 72).
Also adds a startup breadcrumb log line in App.OnStartup carrying the build version + PID so we can correlate a user's log file with a specific commit.
Two simultaneous TeamsISO processes contend over the NDI runtime, the same default sender names, and %APPDATA%\\TeamsISO\\config.json — observed during testing when launchers / shortcuts produced duplicate windows. Add a Local namespace per-user-keyed mutex (Local\\WildDragon.TeamsISO.SingleInstance.<username>) at startup; if a second instance can't claim it, broadcast a registered window message ('WildDragon.TeamsISO.BringToFront') and Shutdown(0). The running instance subscribes to that message via ComponentDispatcher.ThreadFilterMessage and surfaces its main window when received.
Per-user keying lets two different Windows users on the same machine each run their own TeamsISO. Mutex is released and disposed on OnExit.
Verified: Start-Process the exe twice in a row -> only one process remains, with the original window surfaced.
- TeamsISO.App: hand-rolled net8.0-windows WPF csproj since the WPF
template isn't shipped on linux-arm64 .NET SDK; UI is a placeholder
for Phase C.
- TeamsISO.Engine.IntegrationTests: cross-platform xunit project with a
skipped scaffold fact tagged [Trait("requires", "ndi")] for Phase B.
- TeamsISO.Linux.slnf: solution filter for non-Windows CI that excludes
the WPF project (which can only build on Windows).
