fix: keep lock file after cleanup so client always skips

Server holds the lock even after cleanup. Client always sees the lock
and skips bot startup. On crash, stale PID is detected and lock is
cleaned up automatically.

index.ts

@@ -283,7 +283,7 @@ async function runPlugin(ctx: any, options: any) {
       log("Plugin cleaning up...")
       eventController.abort()
       matrix.stop()
-      releaseLock()
+      // Don't release lock — keep it on disk so client always sees it
     }
 
     return cleanup