OAuth session persists via DPAPI; sign-in lives in the Start Stream dialog; add xUnit test project (6 passing)

Services/index.md

@@ -5,7 +5,7 @@ External-facing logic: YouTube API, persistence. See
 
 | File | Purpose |
 |------|---------|
-| `YouTubeAuthService.cs` | OAuth2 via Google: loopback callback (`http://localhost:8765/oauth2/callback`), token exchange, refresh, channel fetch. **Complete — but no token persistence yet** (DPAPI planned) |
+| `YouTubeAuthService.cs` | OAuth2 via Google: loopback callback (`http://localhost:8765/oauth2/callback`), token exchange, refresh, channel fetch. Constructor takes optional `HttpClient` + `sessionChanged` callback (test seam + save hook); session persists via `Helpers/TokenStore` (DPAPI) |
 | `YouTubeStreamService.cs` | Broadcast/stream management via the v3 API (`enableAutoStart/Stop`). **Not yet switched to the `variable` reusable stream** |
 | `YouTubeChatService.cs` | Polls `liveChat/messages`, raises `MessageReceived`; `IDisposable` |
 | `LayoutStore.cs` | SQLite persistence (`Microsoft.Data.Sqlite`) at `%APPDATA%\ytLlive\ytLlive.db`; assets stored as BLOBs keyed by SHA-256 content hash; save/open layout files |