This merge delivers five features: a session switcher for the chat header with mobile-aware dropdown styling and proper ARIA state, mailbox notification events with deep-link highlighting to the unread task, a fix for org chart connector endpoints in wide subtrees, a correction to merge finalize so
Fusion-Task-Id: FN-3800
Merges FN-3008 to add a "fallback-used" notification system: the engine now emits events when AI model fallbacks are triggered, dispatches notifications via ntfy/webhook providers, surfaces a session banner in the dashboard, and exposes a settings toggle to enable or disable these alerts.
Fusion-Task-Id: FN-3008
- Add notification service module with provider abstractions and ntfy provider implementation
- Refactor NtfyNotifier into a compatibility wrapper that delegates task-event delivery to NotificationService
- Initialize and stop NotificationService from ProjectEngine while preserving gridlock notifications via NtfyNotifier
- Export notification APIs from engine index and add focused unit coverage for provider, service, and project-engine wiring
