Toasts: non-blocking notifications replace MessageBoxes + log-only failures (TASK 24)

ai.md

@@ -125,7 +125,7 @@ C# / WPF (.NET 8) following MVVM:
 |------|------|
 | `Models/` | Plain data types — Scene, Source (incl. `ClipShape`, `IsMirrored`, `VideoImageSource`), QualityOption, StreamConfig, StreamHealth, YouTubeChannel, ChatMessage, **Socials (`SocialService` enum + `SocialEntry`/`SocialsConfig` + `SocialServiceIcons`) — the social bar** |
 | `ViewModels/` | MainViewModel — exposes collections + commands for the UI; GoLiveViewModel, ReuseImageViewModel, CameraPickerViewModel, **SocialsDialogViewModel** |
-| `Services/` | YouTube OAuth2, stream/broadcast management, live chat polling, LayoutStore (SQLite), **SocialValidator (`ISocialValidator` seam + `HttpSocialValidator` default)**, **webcam: `VideoFrame` seam + `CameraDeviceInfo`/`ICameraEnumerator`/`ICameraFrameSource` interfaces + `MediaCaptureCameraEnumerator`/`MediaCaptureFrameSource` (WinRT) + `CameraManager`**, **screen capture: `IFullScreenDetector`/`Win32FullScreenDetector` + `IScreenCaptureSource`/`ScreenCaptureFrameSource` (WinRT GraphicsCapture) + `ScreenCaptureManager` + `ScreenCaptureSourceFactory` + `Direct3D11Helper`/`CaptureInterop` (COM bridges)**, **compositor: `SceneCompositor` + `CompositorOptions` + pure `StretchMath` + `StaticPixelCache` (see "Scene compositor")**, **audio: `IAudioSource` seam + `WasapiLoopbackAudioSource`/`WasapiMicAudioSource` (NAudio WASAPI) + `AudioMixer` + pure `AudioLevelMeter`/`WaveToFloat`/`VoiceFilterChain`/`LowShelfFilter`/`HighShelfFilter`/`NoiseGate`/`Compressor`/`AutoDucker`/`AudioRingBuffer`/`TinyResampler` + `MusicPlayer` + `IAudioPipeWriter`/`NamedPipeAudioWriter` (see "Live audio capture")**, **encoder: `IFfmpegEncoder`/`FfmpegEncoder` + `IEncoderProcess`/`FfmpegEncoderProcess` + `IFfmpegLocator`/`FfmpegLocator` + pure `FfmpegArgs`/`FfmpegProgressParser`/`FfmpegEncoderPicker` + the `FramePump` frame producer (see "Live encoder" + "Live frame pipeline")** |
+| `Services/` | YouTube OAuth2, stream/broadcast management, live chat polling, LayoutStore (SQLite), **SocialValidator (`ISocialValidator` seam + `HttpSocialValidator` default)**, **webcam: `VideoFrame` seam + `CameraDeviceInfo`/`ICameraEnumerator`/`ICameraFrameSource` interfaces + `MediaCaptureCameraEnumerator`/`MediaCaptureFrameSource` (WinRT) + `CameraManager`**, **screen capture: `IFullScreenDetector`/`Win32FullScreenDetector` + `IScreenCaptureSource`/`ScreenCaptureFrameSource` (WinRT GraphicsCapture) + `ScreenCaptureManager` + `ScreenCaptureSourceFactory` + `Direct3D11Helper`/`CaptureInterop` (COM bridges)**, **compositor: `SceneCompositor` + `CompositorOptions` + pure `StretchMath` + `StaticPixelCache` (see "Scene compositor")**, **audio: `IAudioSource` seam + `WasapiLoopbackAudioSource`/`WasapiMicAudioSource` (NAudio WASAPI) + `AudioMixer` + pure `AudioLevelMeter`/`WaveToFloat`/`VoiceFilterChain`/`LowShelfFilter`/`HighShelfFilter`/`NoiseGate`/`Compressor`/`AutoDucker`/`AudioRingBuffer`/`TinyResampler` + `MusicPlayer` + `IAudioPipeWriter`/`NamedPipeAudioWriter` (see "Live audio capture")**, **encoder: `IFfmpegEncoder`/`FfmpegEncoder` + `IEncoderProcess`/`FfmpegEncoderProcess` + `IFfmpegLocator`/`FfmpegLocator` + pure `FfmpegArgs`/`FfmpegProgressParser`/`FfmpegEncoderPicker` + the `FramePump` frame producer (see "Live encoder" + "Live frame pipeline")**, **notifications: `INotificationService` seam (`AppNotificationSeverity` Info/Success/Warning/Error) + `NotificationService` (Notification.Wpf toasts, see "Toast notifications")** |
 | `Helpers/` | ViewModelBase (INotifyPropertyChanged), RelayCommand, ImageCache, AppLog (file logger), FocusPreservingListBox, OAuthCredentials, **TokenStore (DPAPI session persistence)**, visibility converters |
 | `Themes/` | `Controls.xaml` — the single dark-theme source, merged once in `App.xaml` (see `Themes/index.md`) |
 | `MainWindow.xaml` | Dark theme; layout: top bar (controls), center (preview), left (scenes/sources), right (chat), bottom (health) |
@@ -611,6 +611,30 @@ never touch slot state).
    Pbgra32→straight-alpha unpremultiply) and the compositor blits it above the flash (see "Live frame
    pipeline").
 
+### Toast notifications (TASK 24 — shipped 2026-08-23, plan in TASKS.md)
+
+Non-blocking user-facing messages replace blocking MessageBoxes. **Seam:** `INotificationService.Show(title,
+message, AppNotificationSeverity)` (`Services/INotificationService.cs`) + `Info/Success/Warning/Error`
+extension methods; `MainViewModel` news up the real `NotificationService` at its field initializer
+(no DI container — the VM is built from XAML). **Library:** `Notification.Wpf` 11.0.0 (Platonenkov fork,
+MIT — notice #10 in `THIRD-PARTY-NOTICES.txt`). Facts that cost a hunt:
+- The `NotificationArea` XAML control registers itself with the manager on `Loaded`; routing matches
+  the area's `Name` against the request's `AreaName` — our host is `x:Name="ToastArea"` in MainWindow's
+  root grid (last child = topmost z-order, `Grid.RowSpan=4`, bottom-right above the footer via
+  `Margin="0,0,12,96"`, outside the preview Viewbox). An unknown AreaName silently drops the toast.
+- `NeverExpires()` sets `ExpirationTime = TimeSpan.MaxValue` (NOT null); `NotificationColor.ToHex()`
+  returns `#AARRGGBB` (alpha prefix).
+- Lifetimes: Info/Success ~4s, Warning ~8s auto-dismiss, Error sticky until dismissed (the pure mapping
+  lives in `NotificationService.BuildRequest` + the `Cards` tint table: slate info `#3a3b52`, green
+  success `#1d5c38`, amber warning `#b8860b`, dark-red error `#8f1f1f` — matching the health-banner language).
+- Calls marshal to the captured Dispatcher (`_dispatcher.Invoke`) — encoder/pump events fire off-thread.
+
+Migrated MessageBoxes: both webcam-acquire warnings, image-read warning, sign-in unsuccessful/failed.
+Promoted from log-only (each keeps its AppLog line): go-live prep failures ×3 (reusable stream,
+broadcast insert, prep exception), frame-pump death while live, mic-missing at startup, premium lapse,
+saved-session refresh failure (sign-out notice). Deliberately left log-only: offline license re-validation
+skip (would spam every launch). Still modal by design: SocialsDialog's slot-delete YesNo confirm.
+
 ### Licensing — do not violate (GA = paid product; see `THIRD-PARTY-NOTICES.txt`)
 
 This product is closed-source and paid. Every third-party component must stay inside the LGPL/BSD/MIT