[$25 BOUNTY] Add stale diagnostic cleanup dry run

[Saiaaax]

Summary

Add a --diagnostic-cleanup flag to build.py that lists stale diagnostic artifacts (those not belonging to the current commit) without deleting them. An explicit --force-cleanup flag is required to actually perform the deletion. Current commit artifacts are always preserved.

Closes #68

Changes

• build.py: Added --diagnostic-cleanup flag (dry-run by default) and --force-cleanup flag for actual deletion
  • New function find_stale_diagnostic_artifacts() scans the diagnostic/ directory for artifacts whose embedded commit ID differs from the current HEAD
  • New function run_diagnostic_cleanup() handles both dry-run listing and force deletion with size reporting
  • Current commit artifacts (including chunked .logd parts) are never removed
  • Updated argparse epilog with cleanup usage examples
• tools/test_stale_cleanup.py: New test file with 10 test cases covering:
  • Current commit artifacts excluded from stale list
  • Other commit artifacts included in stale list
  • Empty and nonexistent directory handling
  • Non-matching file patterns ignored
  • Dry-run does not delete files
  • Force mode deletes stale but preserves current commit
  • Correct stale count in both modes
  • Chunked .logd parts detected as stale for old commits
  • Current commit chunked parts preserved in force mode
• docs/OPERATIONS.md: Added "Diagnostic Artifact Cleanup" section documenting:
  • Overview of stale artifact naming conventions
  • Dry-run mode usage and safety guarantees
  • Force mode usage
  • Test running instructions
  • Example session output

Testing

# Dry-run: list stale artifacts without deleting
python3 build.py --diagnostic-cleanup

# Force: actually delete stale artifacts
python3 build.py --diagnostic-cleanup --force-cleanup

# Run the test suite
python3 tools/test_stale_cleanup.py

All 10 tests pass using temporary diagnostic directories (no real files are modified).

Diagnostic Artifacts

• Diagnostic .logd reference: diagnostic/build-ec966bc5.logd
• Matching metadata: diagnostic/build-ec966bc5.json

Checklist

• Relevant modules affected by these changes build locally
• Tests pass locally
• Diagnostic build log is committed in this PR
• Documentation has been updated, if applicable
• Configuration or schema changes are documented, if applicable
• No generated build artifacts are committed, except the required diagnostic build log
• Changes are scoped to the PR purpose and avoid unrelated cleanup
• Security, privacy, and error-handling implications have been considered

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• I would like to request that my diagnostic build log is removed before merging

Payout address: 0x5253757322092903C2F0a8EfEed592344216CC7E