fix(cleanup): revalidate destructive backend plans

bot_bottle/backend/firecracker/lifecycle_lock.py

@@ -0,0 +1,30 @@
+"""Serialize Firecracker run-directory creation with orphan cleanup."""
+
+from __future__ import annotations
+
+import fcntl
+from contextlib import contextmanager
+from pathlib import Path
+from typing import Generator
+
+from . import util
+
+
+def _lock_path() -> Path:
+    return util.cache_dir() / "run.lifecycle.lock"
+
+
+@contextmanager
+def hold() -> Generator[None]:
+    """Exclude cleanup while a launch directory lacks a visible VMM."""
+    path = _lock_path()
+    path.parent.mkdir(parents=True, exist_ok=True)
+    with path.open("a", encoding="utf-8") as handle:
+        fcntl.flock(handle, fcntl.LOCK_EX)
+        try:
+            yield
+        finally:
+            fcntl.flock(handle, fcntl.LOCK_UN)
+
+
+__all__ = ["hold"]