fix(simulation): cache idle worker state

tests/test_simulation_worker_agent_command.py

@@ -171,6 +171,28 @@ def test_worker_agent_command_dispatch_fails_closed_on_unsafe_envelope() -> None
         )
 
 
+def test_worker_agent_caches_the_absence_of_an_active_run() -> None:
+    class EmptyStore:
+        def __init__(self) -> None:
+            self.list_calls = 0
+
+        def list_runs(self) -> tuple[QualificationRun, ...]:
+            self.list_calls += 1
+            return ()
+
+    agent = object.__new__(SimulationWorkerAgent)
+    store = EmptyStore()
+    agent.__dict__["store"] = store
+
+    first = agent.status()
+    second = agent.status()
+
+    assert first["available"] is True
+    assert first["active_run_id"] is None
+    assert second["active_run_id"] is None
+    assert store.list_calls == 1
+
+
 def test_px4_adapter_maps_speed_to_stock_rover_throttle_without_direct_actuators() -> None:
     publishers = [_Publisher() for _ in range(3)]