[codex] Fix homepage drill hydration mismatch

[CircleQMinh]

Summary

• replace randomized homepage Live Drill selection with deterministic first, middle, and last candidates
• keep the initial SSG output identical to the first browser render
• record the deployment finding and pending production recheck in the SEO plan and handoff

Root cause

The homepage shuffled drill candidates with Math.random() during both static generation and browser hydration. The two renders selected different visible text, causing React hydration error #418.

Impact

The homepage now shows a stable, curriculum-spread set of three drills. This removes the hydration mismatch without changing routing, SEO metadata, persisted state, or deployment behavior.

Validation

• npm run lint
• npm run test:theme-bootstrap
• npm run test:seo
• npm run test:content-route-data
• npm run build
• npm run build:framework
• npm run finalize:framework
• npm run validate:framework
• repeated framework-preview homepage loads produced identical drill titles and zero browser console errors