feat: Implement full-text search for user prompts

- Added functionality to save raw user prompts for full-text search in the newHook function.
- Introduced new search endpoint 'search_user_prompts' to retrieve user prompts using FTS5.
- Created UserPromptRow and UserPromptSearchResult types for handling user prompt data.
- Implemented searchUserPrompts method in SessionSearch class to perform FTS5 queries.
- Created user_prompts table with FTS5 support and necessary triggers for data synchronization.
- Updated SessionStore to include methods for saving user prompts and managing the new table.

src/hooks/new.ts

@@ -34,6 +34,10 @@ export async function newHook(input?: UserPromptSubmitInput): Promise<void> {
     // Just save session_id for indexing - no validation, no state management
     const sessionDbId = db.createSDKSession(session_id, project, prompt);
     const promptNumber = db.incrementPromptCounter(sessionDbId);
+
+    // Save raw user prompt for full-text search
+    db.saveUserPrompt(session_id, promptNumber, prompt);
+
     console.error(`[new-hook] Session ${sessionDbId}, prompt #${promptNumber}`);
 
     // Get fixed port