chore: prepare 0.0.28 release

[freshtechbro]

Summary

• Bump package, lockfile, and extension metadata to 0.0.28.
• Add the 0.0.28 release evidence ledger.
• Add focused social/macro/challenge coverage so the release coverage gate clears the 97% branch threshold.

Validation

• npm run version:check
• node scripts/docs-drift-check.mjs
• node scripts/chrome-store-compliance-check.mjs
• node scripts/audit-zombie-files.mjs
• npm run lint
• npm run typecheck
• npm run build
• npm run extension:build
• npm run test
• npm run test:release-gate
• ./skills/opendevbrowser-best-practices/scripts/validate-skill-assets.sh
• npx opendevbrowser --help
• npx opendevbrowser help
• npm pack --pack-destination /tmp
• npm run extension:pack
• git diff --check

Release Notes

• npm latest is still 0.0.27 before publish.
• GitHub release v0.0.28 does not exist yet.
• Post-merge release still needs npm publish verification, GitHub release asset verification, and first-time registry consumer smoke.