fix: support multiple Feishu connections

[huboqiang]

Summary

• support multiple Feishu long-connection profiles without cross-thread event loop collisions
• validate Feishu profile credentials independently and retry transient Feishu HTTP delivery failures
• prevent stale runner readiness from overriding successful connector start/queue acknowledgements

Tests

• HOME=/private/tmp/deepscientist-test-home runtime/python-env/bin/python -m pytest tests/test_feishu_long_connection.py::test_feishu_sdk_bundle_installs_thread_loop_proxy tests/test_connector_profiles.py::test_feishu_delivery_retries_transient_urlopen_error tests/test_config_testing.py::test_runner_live_config_test_persists_startup_probe_state tests/test_config_testing.py::test_feishu_profiles_validate_profile_credentials_without_top_level_secret tests/test_generic_connectors.py::test_generic_connector_ack_prefers_started_state_over_stale_runner_readiness
• runtime/python-env/bin/python -m compileall src/deepscientist
• git diff --check

Fixes #89