fix(lark): keep connection lookup off event loop

Move the Lark SDK synchronous connection URL lookup off the main asyncio loop, serialize reconnects, and cover the incident with a non-blocking regression test.

tests/unit_tests/platform/test_lark_ws_nonblocking.py

@@ -0,0 +1,39 @@
+import asyncio
+import threading
+
+import pytest
+
+from langbot.pkg.platform.sources.lark import NonBlockingLarkWSClient
+
+
+@pytest.mark.asyncio
+async def test_lark_connection_url_lookup_does_not_block_main_event_loop(monkeypatch):
+    client = NonBlockingLarkWSClient('app-id', 'app-secret')
+    lookup_started = threading.Event()
+    release_lookup = threading.Event()
+    base_connect_urls: list[str] = []
+
+    def blocking_get_conn_url() -> str:
+        lookup_started.set()
+        if not release_lookup.wait(timeout=2):
+            raise TimeoutError('test did not release the connection lookup')
+        return 'wss://example.invalid/connect?device_id=device&service_id=service'
+
+    async def fake_base_connect(self):
+        base_connect_urls.append(self._get_conn_url())
+
+    monkeypatch.setattr(client, '_get_conn_url', blocking_get_conn_url)
+    monkeypatch.setattr('lark_oapi.ws.Client._connect', fake_base_connect)
+
+    connect_task = asyncio.create_task(client._connect())
+    await asyncio.wait_for(asyncio.to_thread(lookup_started.wait, 1), timeout=1)
+
+    # If the SDK's synchronous requests.post still runs on the event-loop
+    # thread, this sleep cannot complete until release_lookup is set.
+    await asyncio.wait_for(asyncio.sleep(0.01), timeout=0.1)
+    assert not connect_task.done()
+
+    release_lookup.set()
+    await asyncio.wait_for(connect_task, timeout=1)
+
+    assert base_connect_urls == ['wss://example.invalid/connect?device_id=device&service_id=service']