fix: replace hardcoded /Users/user fallback with os.homedir()

The HOME_DIR fallback '/Users/user' is macOS-specific and incorrect.
Use os.homedir() from Node's os module which works cross-platform
and returns the actual home directory from /etc/passwd on Linux.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/config.ts

@@ -1,3 +1,4 @@
+import os from 'os';
 import path from 'path';
 
 import { readEnvFile } from './env.js';
@@ -19,7 +20,7 @@ export const SCHEDULER_POLL_INTERVAL = 60000;
 
 // Absolute paths needed for container mounts
 const PROJECT_ROOT = process.cwd();
-const HOME_DIR = process.env.HOME || '/Users/user';
+const HOME_DIR = process.env.HOME || os.homedir();
 
 // Mount security: allowlist stored OUTSIDE project root, never mounted into containers
 export const MOUNT_ALLOWLIST_PATH = path.join(