feat: add reliable trigger and worker message blocks

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a03397-4d51-7fd1-8ff2-946eb22ea2bc

tests/test_line_limits.py

@@ -25,6 +25,7 @@ def test_window_counters_survive_reopen_and_isolate_repositories(tmp_path, monke
         notify=blocked.append,
     )
     assert left.inspect_worker_line("To:target: blocked") is None
+    assert left.inspect_worker_line("") is None
     assert "lines of messages" in blocked[-1]
 
 
@@ -43,7 +44,8 @@ def test_atomic_message_admission_does_not_cross_limit(tmp_path, monkeypatch):
                 BrokerIdentity("session-1", "source"),
                 limits=(1, 100, 100),
             )
-            return broker.inspect_worker_line(f"To:target: {body}") is not None
+            broker.inspect_worker_line(f"To:target: {body}")
+            return broker.inspect_worker_line("") is not None
         finally:
             store.close()