Add docs/go.sum (Hextra v0.12.3 checksums) produced by hugo mod tidy.
Update docs/go.mod with the resolved module version.
Ignore docs/.hugo_build.lock, docs/public/, and docs/resources/ —
all are generated by Hugo locally and not needed in the repo.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>