feat(quality): add browser and changelog gates

[ericyangpan]

Summary

• add Playwright smoke coverage for search-to-detail, locale switching, and persistent model comparison
• require browser smoke and manifest changelog validation in CI
• generate the first structured changelog entry from manifest diffs and document the workflow
• fix search category translation lookup exposed by browser testing

Validation

• npm run biome:check
• npm run spell
• npm run type-check
• npm run test:ci
• npm run test:e2e
• npm run data-health:check
• npm run changelog:check -- --base=origin/main
• npm run generate + generated-source diff check
• npm run build

[github-actions]

Preview deployment

Status	URL
Ready	https://pr-145-aicodingstack.pr-preview.workers.dev

Commit: b0c3fb8
Updated: 2026-07-17T23:38:33.604Z

[github-actions]

Preview deployment cleaned up

The preview deployment for PR #145 has been removed.