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/new.ts

@@ -0,0 +1,60 @@
+import { HooksDatabase } from '../services/sqlite/HooksDatabase.js';
+import path from 'path';
+import { spawn } from 'child_process';
+
+export interface UserPromptSubmitInput {
+  session_id: string;
+  cwd: string;
+  prompt: string;
+  [key: string]: any;
+}
+
+/**
+ * New Hook - UserPromptSubmit
+ * Initializes SDK memory session in background
+ */
+export function newHook(input: UserPromptSubmitInput): void {
+  try {
+    const { session_id, cwd, prompt } = input;
+
+    // Extract project from cwd
+    const project = path.basename(cwd);
+
+    // Check if session already exists
+    const db = new HooksDatabase();
+    const existing = db.findActiveSDKSession(session_id);
+
+    if (existing) {
+      // Session already initialized, just continue
+      db.close();
+      console.log('{"continue": true, "suppressOutput": true}');
+      process.exit(0);
+    }
+
+    // Create SDK session record
+    const sessionId = db.createSDKSession(session_id, project, prompt);
+    db.close();
+
+    // Start SDK worker in background
+    // The SDK worker will be implemented in a separate file
+    // For now, we just create the session record
+
+    // TODO: Spawn SDK worker as detached process
+    // const workerPath = path.join(__dirname, '..', 'sdk', 'worker.js');
+    // const child = spawn('bun', [workerPath, sessionId.toString()], {
+    //   detached: true,
+    //   stdio: 'ignore'
+    // });
+    // child.unref();
+
+    // Output hook response
+    console.log('{"continue": true, "suppressOutput": true}');
+    process.exit(0);
+
+  } catch (error: any) {
+    // On error, don't block Claude Code
+    console.error(`[claude-mem new error: ${error.message}]`);
+    console.log('{"continue": true, "suppressOutput": true}');
+    process.exit(0);
+  }
+}