fix(socket_mode): check the effective log level in debug guards

[Shubham-Padkonde]

Fixes the Socket Mode part of #1957.

The debug guards compared logger.level, which stays NOTSET unless a level is set on that exact logger, so the guarded messages (including debug_redacted_message_string(message) for every inbound message) were built even when DEBUG was disabled through a parent logger. They now use isEnabledFor(logging.DEBUG), which follows the effective level.

I kept this to slack_sdk/socket_mode/; the same pattern in the other modules can follow separately if you want it project-wide.

The added test checks that the message is not built when a parent logger is at INFO and is built at DEBUG; it fails before this change. The Socket Mode test suites (sync and async), ruff and mypy pass.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.15%. Comparing base (b9f4666) to head (7852bf0).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
slack_sdk/socket_mode/aiohttp/__init__.py	86.66%	2 Missing ⚠️
slack_sdk/socket_mode/websockets/__init__.py	81.81%	2 Missing ⚠️
slack_sdk/socket_mode/builtin/client.py	75.00%	1 Missing ⚠️
slack_sdk/socket_mode/websocket_client/__init__.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1965   +/-   ##
=======================================
  Coverage   84.15%   84.15%           
=======================================
  Files         118      118           
  Lines       13566    13566           
=======================================
  Hits        11416    11416           
  Misses       2150     2150           

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[AmyScript]

Nice fix. logger.level stays NOTSET (0) unless a level is set on that exact logger, so level <= DEBUG was effectively always true and the guarded strings (notably debug_redacted_message_string(message) on every inbound message) were built regardless of the effective level. isEnabledFor() follows getEffectiveLevel() and also respects logging.disable(). It's strictly safe too. Test genuinely fails before the change. LGTM. ✅

Non-blocking follow-ups (no need to hold this PR):

• Worth a quick rg 'logger\.level\s*(<=|<|==)\s*logging\.' slack_sdk/socket_mode/
  just to confirm nothing in these modules slipped through.
• Adding an async-path test case wouldn't hurt