feat: Implement Phase 1 of SDK agent architecture with hook integration

- Added CLI commands for context, new session, save observation, and summary.
- Created HooksDatabase for managing SDK sessions and observations.
- Implemented migration 004 to add new tables: sdk_sessions, observation_queue, observations, and session_summaries.
- Developed hook functions for context display, session initialization, observation queuing, and session finalization.
- Added comprehensive tests for database schema and hook functionality.
- Documented Phase 1 implementation in PHASE1-COMPLETE.md.

src/hooks/index.ts

@@ -0,0 +1,4 @@
+export { contextHook } from './context.js';
+export { saveHook } from './save.js';
+export { newHook } from './new.js';
+export { summaryHook } from './summary.js';