fix(builder): use RLock to prevent deadlock in BuildState

app.py

@@ -238,7 +238,7 @@ class BuildState:
     """Thread-safe build state manager with history."""
 
     def __init__(self, max_history: int = 50) -> None:
-        self._lock = threading.Lock()
+        self._lock = threading.RLock()
         self._current: Build | None = None
         self._history: deque[Build] = deque(maxlen=max_history)
         self._logs: deque[str] = deque(maxlen=500)