fix: propagate Socket Mode retry_attempt and retry_reason to BoltRequest headers

[SAY-5]

Summary

In Socket Mode, SocketModeRequest.retry_attempt and SocketModeRequest.retry_reason were dropped when building the Bolt request, so middleware and listeners could not detect Events API retries the way they can in HTTP mode. This synthesizes the x-slack-retry-num / x-slack-retry-reason headers from the envelope so existing retry detection logic works unchanged under Socket Mode. Closes #1484.

Testing

Run python -m pytest tests/adapter_tests/socket_mode/test_internals.py tests/scenario_tests/test_events_socket_mode.py.

Category

• slack_bolt.App and/or its core components
• slack_bolt.async_app.AsyncApp and/or its core components
• Adapters in slack_bolt.adapter
• Document pages under /docs
• Others

Requirements

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run ./scripts/install_all_and_run_tests.sh after making the changes.

Note: I have not yet signed the Salesforce CLA; happy to do so if this is something you would like to accept.