test: model token flushes in the persistence race fixture

tests/run_agent/test_run_agent.py

@@ -126,8 +126,12 @@ def test_direct_session_db_flushes_share_marker_claim(agent):
             self.entered = threading.Event()
             self.release = threading.Event()
             self.calls = 0
+            self.token_flushes = 0
             self._lock = threading.Lock()
 
+        def flush_token_counts(self):
+            self.token_flushes += 1
+
         def append_message(self, **kwargs):
             with self._lock:
                 self.calls += 1
@@ -178,6 +182,7 @@ def test_direct_session_db_flushes_share_marker_claim(agent):
     assert not normal.is_alive()
     assert not direct.is_alive()
     assert db.rows == ["exactly once"]
+    assert db.token_flushes == 1
 
 
 def test_malformed_memory_config_still_builds_default_store():