ks-home website contracts and static generation foundation

Step-900 Slice-910 + Slice-920 includes:

• canonical route map and URL policy
• navigation/footer contract
• content source contract (../ks-content as source of truth)
• markdown frontmatter schema checks
• landing/home experience sections + CTA telemetry hook
• leaderboard experience with loading/empty/error/stale states
• leaderboard payload contract (contracts/leaderboard-contract.json)
• static generation scaffold and smoke/e2e/a11y checks for /, /leaderboard, /rules

Commands

npm ci
npm run lint
npm run test -- --runInBand --watch=false
npm run test:coverage:check -- --lines 82 --functions 82 --branches 78 --statements 82
npm run test:e2e -- --grep "home|leaderboard"
npm run test:smoke -- --routes=/,/leaderboard,/rules
npm run test:a11y -- --routes=/,/leaderboard
npm run test:visual -- --suite=marketing-core
npm run routes:validate
npm run content:schema:check
npm run content:source-contract:check
npm run build
npm run serve:prod -- --host 127.0.0.1 --port 4180

The production deployment on rpi-server-02 serves the generated dist/ output directly via npm run serve:prod; it does not use Vite preview.