fix/agents md relative links

Fix broken relative links in the bundled AGENTS.md guides.

• react-view-transitions: 25 links in the compiled AGENTS.md (patterns.md, css-recipes.md, nextjs.md, troubleshooting.md, implementation.md, ../SKILL.md) resolved beside the file instead of under references/ — now corrected.
• react-best-practices: build.ts now rewrites rule-relative ./xxx.md links to ./rules/xxx.md when generating AGENTS.md; regenerated output fixes 3 broken links and prevents recurrence.