Notification preferences, diagnostics, and test coverage.
- Sound alerts, sound variant (pop/ding/soft), and visual badge preferences now sync to the server alongside desktop notification toggle — no database migration required.
- User settings Notifications card includes sound and visual badge toggles with a sound variant selector.
- Collapsible notification diagnostics panel in user settings shows browser permission status, device record, local preferences, tab visibility state, and a test sound button.
- 31 new unit tests for
browser-message-notifications.tscovering device record persistence, permission detection, native notification creation, and error paths. - Notification stack architecture handoff document added at
planning/design/.