[codex] Add repository polish

[dangercharlie]

Summary

• Adds a minimal GitHub Actions workflow that validates the extension, runs the lint alias, builds the ZIP, and inspects its contents.
• Adds release and workflow badges to the README.
• Adds a Known Limitations section so the project is clearer about tested scope and metadata boundaries.

Verification

• npm run validate:extension - passed
• npm run lint - passed
• npm run zip - passed
• unzip -l dist/YT_Metadata_Pro_Extension.zip - confirmed expected extension files
• git diff --check - passed

Repo Metadata

Also updated GitHub repo description and topics.