Allow /stop without target argument

tests/test_slack_handler.py

@@ -111,7 +111,7 @@ def test_start_command_normalizes_target(monkeypatch) -> None:
     assert called == [("start", "claude", "C1")]
 
 
-def test_stop_command_routes_target_from_text(monkeypatch) -> None:
+def test_stop_command_ignores_target_text(monkeypatch) -> None:
     handler = _build_handler(monkeypatch)
     called = _capture_commands(handler)
 
@@ -121,7 +121,21 @@ def test_stop_command_routes_target_from_text(monkeypatch) -> None:
         {"user_id": "U1", "channel_id": "C1", "text": "claude"},
     )
 
-    assert called == [("stop", "claude", "C1")]
+    assert called == [("stop", "", "C1")]
+
+
+def test_stop_command_without_target_routes_immediately(monkeypatch) -> None:
+    handler = _build_handler(monkeypatch)
+    called = _capture_commands(handler)
+
+    stop_handler = handler.app.command_handlers["/stop"]
+    stop_handler(
+        lambda: None,
+        {"user_id": "U1", "channel_id": "C1", "text": ""},
+    )
+
+    assert called == [("stop", "", "C1")]
+    assert handler.app.client.messages == []
 
 
 def test_invalid_target_sends_warning_message(monkeypatch) -> None: