fix: ensure data directory exists before writing PM2 migration marker

Fixes ENOENT error on first install when ~/.claude-mem/ directory
doesn't exist yet. The startWorker() function tried to write the
.pm2-migrated marker file without first creating the parent directory.

Fixes #259

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/shared/worker-utils.ts

@@ -1,7 +1,7 @@
 import path from "path";
 import { homedir } from "os";
 import { spawnSync } from "child_process";
-import { existsSync, writeFileSync, readFileSync } from "fs";
+import { existsSync, writeFileSync, readFileSync, mkdirSync } from "fs";
 import { logger } from "../utils/logger.js";
 import { HOOK_TIMEOUTS, getTimeout } from "./hook-constants.js";
 import { ProcessManager } from "../services/process/ProcessManager.js";
@@ -150,7 +150,11 @@ async function ensureWorkerVersionMatches(): Promise<void> {
  */
 async function startWorker(): Promise<boolean> {
   // Clean up legacy PM2 (one-time migration)
-  const pm2MigratedMarker = path.join(SettingsDefaultsManager.get('CLAUDE_MEM_DATA_DIR'), '.pm2-migrated');
+  const dataDir = SettingsDefaultsManager.get('CLAUDE_MEM_DATA_DIR');
+  const pm2MigratedMarker = path.join(dataDir, '.pm2-migrated');
+
+  // Ensure data directory exists (may not exist on fresh install)
+  mkdirSync(dataDir, { recursive: true });
 
   if (!existsSync(pm2MigratedMarker)) {
     try {