Fix React Effect remount guidance

[lidorcg]

Fixes #10.

What changed

• Replaced the ref-guarded "once on mount" recommendation with React's setup → cleanup → setup lifecycle invariant.
• Routed app initialization to module scope or a framework boot hook, consistent with the skill's existing Effects taxonomy.
• Bumped the React skill patch version from 1.2.4 to 1.2.5.

This keeps the render-purity rule focused while ensuring Effect guidance agrees with React 19.2 Strict Mode behavior.

Official references:

• https://react.dev/reference/react/useEffect
• https://react.dev/learn/synchronizing-with-effects
• https://react.dev/learn/you-might-not-need-an-effect

Validation

• scripts/skills-ref validate skills/.curated/react — passed with 0 warnings
• npm run validate — 205/205 skills passed
• npm test — 11/11 tests passed
• node scripts/check-versions.mjs — React 1.2.5 reports OK
• scripts/generate-readme-tables --update — no README diff
• isolated npx skills add ... --skill react --agent codex --yes --copy — installed the corrected reference byte-for-byte

Authoring audit

Rule	Observable check
Minimal, tracked source change	Diff contains only the affected reference and metadata.json
Preserve current React semantics	Wording matches React's complete-dependency and mirrored-cleanup contract
Erase rejected-design residue	The active React skill contains no ref-guarded "once on mount" recommendation
Keep examples and routing coherent	Existing app-initialization and cleanup references agree with the replacement
Keep generated navigation current	README generator produced no diff