refactor(bus): type outbound runtime events

tests/session/test_turn_continuation.py

@@ -49,10 +49,6 @@ async def test_maybe_continue_turn_queues_internal_message():
                 "message_id": "msg-1",
                 "origin_message_id": "msg-0",
                 "_wants_stream": True,
-                "_stream_id": "stream-1",
-                "_stream_delta": True,
-                "_stream_end": True,
-                "_resuming": True,
                 "webui": True,
             },
         ),
@@ -78,10 +74,6 @@ async def test_maybe_continue_turn_queues_internal_message():
     assert queued.metadata["message_id"] == "msg-1"
     assert queued.metadata["origin_message_id"] == "msg-0"
     assert queued.metadata["_wants_stream"] is True
-    assert "_stream_id" not in queued.metadata
-    assert "_stream_delta" not in queued.metadata
-    assert "_stream_end" not in queued.metadata
-    assert "_resuming" not in queued.metadata
     assert "Finish the migration." in queued.content
     assert ctx.all_messages == messages[:-1]
     assert ctx.final_content == ""