refactor: Complete rewrite of worker-utils.ts and cleanup of worker-service.ts

- Removed fragile PM2 string parsing and replaced with direct PM2 restart logic.
- Eliminated silent error handling in worker-utils.ts for better error visibility.
- Extracted duplicated session auto-creation logic into a new helper method getOrCreateSession() in worker-service.ts.
- Centralized configuration values and replaced magic numbers with named constants.
- Updated health check logic to ensure worker is restarted if unhealthy.
- Removed unnecessary getWorkerPort() wrapper function.
- Improved overall code quality and maintainability by applying DRY and YAGNI principles.

src/hooks/cleanup-hook.ts

@@ -5,6 +5,7 @@
 
 import { stdin } from 'process';
 import { SessionStore } from '../services/sqlite/SessionStore.js';
+import { getWorkerPort } from '../shared/worker-utils.js';
 
 export interface SessionEndInput {
   session_id: string;
@@ -71,7 +72,7 @@ async function cleanupHook(input?: SessionEndInput): Promise<void> {
 
   // Tell worker to stop spinner
   try {
-    const workerPort = session.worker_port || 37777;
+    const workerPort = session.worker_port || getWorkerPort();
     await fetch(`http://127.0.0.1:${workerPort}/sessions/${session.id}/complete`, {
       method: 'POST',
       signal: AbortSignal.timeout(1000)