* feat: add context window usage display to task session
- Add TokenUsageDisplay component showing context window usage as a horizontal progress bar
- Add useSessionContextWindow hook with proper Zustand reactivity (subscribe to primitives)
- Add ContextWindowState to store with setContextWindow action
- Backend: propagate context_window data through orchestrator, watcher, and lifecycle events
- WebSocket handler extracts context_window from session.state_changed metadata
- Display positioned on left side of action bar, updates in real-time
* refactor: remove agent stream event WebSocket broadcasting
Agent stream events (message_chunk, tool_call, etc.) are now handled
internally by the lifecycle manager rather than being broadcast to
the frontend. Messages are accumulated and flushed as comments at
step boundaries.
João Salavisa