[codex] Allow bundled strategy config in LongBridge env sync

[Pigbibi]

Summary

• detect bundled strategy config files while resolving env-sync requirements
• do not require LONGBRIDGE_STRATEGY_CONFIG_PATH when the selected strategy has a bundled config in the repo
• keep the explicit env override path supported for external configs

Validation

• bash tests/test_sync_cloud_run_env_workflow.sh
• PYTHONPATH=.:../UsEquityStrategies/src:../QuantPlatformKit/src uv run --with pytest --with pandas --with numpy --with pytz --with requests --with flask --with pandas-market-calendars --with longport python -m unittest tests.test_runtime_config_support -v
• git diff --check