docs: sync Interactive Surface 1.5 release status

[Foscat]

Summary

• updates public docs from release-candidate wording to published 1.5.0 status
• keeps publish/tag/release actions approval-gated for future releases
• adds documentation contract coverage so public docs cannot regress to release-candidate wording

Current branch state

• Head: bf05e8c183d6bbb456997af8a6e2ca6da67f4c46
• Base: main after the merged interactive-surface-css@1.5.0 release
• Registry state: interactive-surface-css@1.5.0 is published

Verification

• Fresh local gate passed: npm run validate:ci
  • npm run check:no-hex-colors — no hex color literals found in 5 checked stylesheets
  • npm run lint:css
  • npm run check:public
  • npm run build
  • npm run check:generated
  • npm run test:contracts — 20 passed
  • npm run test:package — 5 passed
  • npm run pack:dry — interactive-surface-css-1.5.0.tgz, 25 files, shasum dc293488eba17c07ab4750dca2deb9694e4d44e7
  • npm run audit — found 0 vulnerabilities
• Setup preflight: npm ci --ignore-scripts — 0 vulnerabilities
• npm run format:check — all matched files use Prettier code style
• git diff --check
• GitHub CI and CodeQL are green on the current branch head

No npm publish, tag, or GitHub release is performed by this PR.