ServiceProvider is never disposed - PLC teardown code is unreachable in production

[mrcsin]

Summary

Program.StartupAsync builds the container (Program.cs, services.BuildServiceProvider()) and nothing ever disposes it — there is no desktop.ShutdownRequested/Exit hook and App.Run does not dispose the provider after StartWithClassicDesktopLifetime returns.

Impact

The carefully written teardown paths never run in production (only tests exercise them):

• S7Service.DisposeAsync — graceful PLC disconnect;
• PlcLifecycleManager.Dispose — sync-ownership lease release;
• PlcSyncCoordinator.Dispose — waits out a pending sync.

Concretely: a recipe edit debounced in the last second before exit is silently dropped; the ownership lock-file handle is released by the OS, not by the code that owns it; the PLC sees a TCP reset instead of a clean disconnect.

Suggested fix

Dispose the provider after StartWithClassicDesktopLifetime returns (async disposables via DisposeAsync), or hook IClassicDesktopStyleApplicationLifetime.ShutdownRequested. Verify the shutdown order tolerates the PLC being unreachable (teardown must not block exit — bound it with a timeout).

Related: singleton view models (MainWindowViewModel, RecipeCoordinator) also implement IDisposable and are equally unreachable; container disposal covers them for free.