fix(node): route capture/record toasts through App.ShowToast

[AlexAlves87]

Summary

NodeService had its own ShowToast helper that called ToastContentBuilder.Show() directly. This bypassed the sound preference (None / Subtle / Default) and the 30-second deduplication window both implemented in App.ShowToast.

All screen-capture, screen-record, and camera toasts were affected — including toasts that fire on attacker-controllable triggers (screen.snapshot throttled once per 10 s).

Changes

• Remove NodeService.ShowToast
• Add NodeService.ToastRequested event (EventHandler<ToastContentBuilder>)
• Replace all direct toast calls in capture/record handlers with ToastRequested?.Invoke
• Subscribe in App and delegate to App.ShowToast, so sound preferences and dedup are honoured

Fixes #342.

Co-Authored-By: Claude Sonnet 4.6 noreply@anthropic.com

[shanselman]

Good direction routing these through App.ShowToast, but this changes the failure semantics for node capture/record commands.

NodeService.ShowToast() used to swallow toast errors. After this PR, ToastRequested?.Invoke(...) can throw synchronously because App.ShowToast(builder) ultimately calls builder.Show() without a local try/catch. That means a toast-platform failure can now fail screen.snapshot, replace the intended camera InvalidOperationException, or mask the original capture/recording error.

Suggested fix: keep notification failures non-fatal at the app boundary:

private void OnNodeToastRequested(object? sender, ToastContentBuilder builder)
{
    try
    {
        ShowToast(builder);
    }
    catch (Exception ex)
    {
        Logger.Warn($"Failed to show node toast: {ex.Message}");
    }
}

A small unit seam/test would be ideal, but the main requirement is that toast delivery failures must not change node command results.

[AlexAlves87]

Added the try/catch so toast failures are non-fatal. Also fixed a thread-safety gap: the capture/record handlers fire ToastRequested from async workers, but ShowToast touches _recentToastKeys (a plain Dictionary) without synchronisation. Marshalled OnNodeToastRequested through _dispatcherQueue, consistent with how OnSystemNotify already handles this. Added a unit seam (NonFatalAction.Run) with three tests covering the non-fatal dispatch behaviour.