feat(predict-rlm): reattachable persistent sandboxes + on-demand interrupt (#41, #42)

src/predict_rlm/backends/base.py

@@ -78,6 +78,21 @@ def async_tool_callback(self):
         finally:
             _TOOL_CALLBACK_GATES.reset(token)
 
+    def is_running(self) -> bool:
+        """Whether a top-level execution currently holds the gate."""
+        with self._condition:
+            return self._running
+
+    def wait_until_idle(self, timeout: float | None = None) -> bool:
+        """Block until no top-level execution holds the gate.
+
+        Returns ``True`` once the gate is idle, or ``False`` if ``timeout``
+        elapsed first. Callers must be on a different thread than the one
+        holding the gate (the executing worker), otherwise this deadlocks.
+        """
+        with self._condition:
+            return self._condition.wait_for(lambda: not self._running, timeout)
+
     def _acquire(self) -> None:
         with self._condition:
             while self._running: