[codex] Add legacy uppercase marker audit

[zack-bolich]

Summary

Adds tools/legacy_caps_audit.py to enforce that files containing legacy references also include an uppercase LEGACY marker in a comment-like line. Adds focused LEGACY audit marker comments to the files flagged by the new audit so the script exits cleanly.

Fixes #12.

Changes

• Added a repository audit script at tools/legacy_caps_audit.py.
• The script scans source, docs, config, and script files while excluding generated/vendor/build-style directories.
• Added minimal uppercase LEGACY marker comments to files that already contained legacy references.

Testing

• python tools\legacy_caps_audit.py on Windows: passed.
• python3 tools/legacy_caps_audit.py in Ubuntu WSL: passed.
• python -m py_compile tools\legacy_caps_audit.py: passed.
• git diff --check: passed.

Build diagnostic note

I attempted the required python3 build.py validation in both Windows and Ubuntu WSL. In both environments, the build reached Checking encryptly diagnostics... and stalled in the encryptly diagnostic step. Because that step did not finish, I could not produce a new real diagnostic/build-*.logd artifact for this submission. The repository currently only contains the existing placeholder diagnostic/build-00000000.logd and diagnostic/build-00000000.json, which I did not use as new validation evidence.

Checklist

• Relevant modules affected by these changes build locally where applicable
• 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