[codex] Require explicit strategy profile selection

[Pigbibi]

Summary

• require STRATEGY_PROFILE to be set explicitly for the LongBridge runtime
• remove default and rollback profile roles from the platform profile status output
• update docs and tests for explicit profile selection
• set an explicit profile in the shared chat fallback test so full CI matches the new runtime contract

Validation

• ../LongBridgePlatform/.venv/bin/python -m pytest tests/test_shared_chat_id_fallback.py tests/test_runtime_config_support.py
• ../LongBridgePlatform/.venv/bin/python -m unittest discover -s tests -v