fix(socket-mode): only release connect_operation_lock in send_message when acquired

[dylanpulver]

Summary

#1926 fixed if self.connect_operation_lock.locked() is True: release() in AsyncBaseSocketModeClient.connect_to_new_endpoint. The same shape is still in send_message() in both async backends.

websockets is the worse of the two: its retry block never acquires the lock, it only releases it in finally. So while a reconnect holds the lock, any send_message() that falls into the retry path releases the reconnect's lock, and a second reconnect can start while the first is still running. The aiohttp sibling does acquire here, which is what makes the omission visible.

aiohttp acquires but releases based on locked(), so a task cancelled while awaiting acquire() releases whichever task does hold the lock. That is the case #1926 describes.

Both now track whether this task acquired. The three sync paths (builtin, websocket_client, rtm_v2) take the lock with with and cannot get this wrong, so they needed no change.

Testing

A test per backend, in the style of the one added with #1926: another task holds the lock, send_message() hits its retry path and is cancelled, and the lock must still be held afterwards. Each fails on main and passes with the change.

• pytest tests/slack_sdk_async/socket_mode/ — 22 passed (20 before these two)
• ./scripts/lint.sh — ruff format --check 455 files clean, ruff check slack/ slack_sdk/ clean
• mypy --config-file pyproject.toml on both changed modules — no issues

I ran those individually rather than through ./scripts/run_validation.sh, so I have left that box unchecked.

Category

• slack_sdk.web.WebClient (sync/async) (Web API client)
• slack_sdk.webhook.WebhookClient (sync/async) (Incoming Webhook, response_url sender)
• slack_sdk.socket_mode (Socket Mode client)
• slack_sdk.signature (Request Signature Verifier)
• slack_sdk.oauth (OAuth Flow Utilities)
• slack_sdk.models (UI component builders)
• slack_sdk.scim (SCIM API client)
• slack_sdk.audit_logs (Audit Logs API client)
• slack_sdk.rtm_v2 (RTM client)
• /docs (Documents)
• /tutorial (PythOnBoardingBot tutorial)
• tests/integration_tests (Automated tests for this library)

Requirements

• 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 python3 -m venv .venv && source .venv/bin/activate && ./scripts/run_validation.sh after making the changes.

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @dylanpulver to sign the Salesforce Inc. Contributor License Agreement.