Process fork hang fixed; CI Visibility retries and git contention resolved

Bug Fixes

• tracing: This fix resolves a rare issue that could cause an application to hang after forking a child process.

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• CI Visibility: Fixes spurious git warnings when running tests with pytest-xdist. Simultaneous git fetch --update-shallow calls now retry with exponential back-off on .git/shallow.lock contention, skip the fetch entirely once a sibling worker has already unshallowed the repository, and run under the C locale so the contention check is robust against non-English git messages. git merge-base is deferred until after unshallowing so the required commits are available locally.

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• CI Visibility: This fix resolves an issue where quarantined tests were not retried by Auto Test Retry (ATR).