WA-NEW-002: Guard callback workers + truncate all Mongoid clients in tests

[kitcommerce]

Extracted from stacked PRs #630/#631.

Summary (from commit 966cf2e):

• Guard callback workers
• Truncate all Mongoid clients in tests

Goal: land as its own minimal PR targeting next so downstream PRs can rebase cleanly.

[kitcommerce]

Build Gate Failed

The following checks failed. Fix and push to re-enter review.

rubocop

<<

Branch: wa-new-002-guard-callback-workers
PR: #646

[kitcommerce]

Build Gate Failed (details)

rubocop

Rakefile:80:11 Layout/SpaceAroundOperators Operator `<<` should be surrounded by a single space.
core/lib/workarea/configuration.rb:955:7 Layout/CommentIndentation Incorrect indentation detected (column 6 instead of 0).
core/lib/workarea/ext/freedom_patches/bson_document.rb:10:1 Layout/TrailingWhitespace Trailing whitespace detected.
core/test/lib/workarea/elasticsearch/document_test.rb:114:1 Layout/TrailingWhitespace Trailing whitespace detected.

Branch: wa-new-002-guard-callback-workers
PR: #646

Once fixed + pushed, re-apply status:ready-for-review and the dispatcher will rerun build gate + review waves.