### What this PR does

Before this PR:
No React/Next.js performance best practices skill available for AI
coding agents.

After this PR:
Adds the `vercel-react-best-practices` skill from
`vercel-labs/agent-skills`, providing 60+ React and Next.js performance
optimization rules covering rendering, re-renders, bundling, async
patterns, server components, and JS performance.

### Why we need it and why it was done in this way

The following tradeoffs were made:
- This skill includes ~8 Next.js server-specific rules (`server-*`,
`async-api-routes`) that are not applicable to our Electron + React
project. We chose to keep them rather than fork/trim the skill, since:
(1) AI agents will naturally ignore irrelevant rules based on context,
(2) keeping the full skill makes future upstream updates easier, and (3)
the ~50 React/JS/rendering/bundle rules provide significant value for
our codebase.

The following alternatives were considered:
- Forking the skill and removing Next.js-specific rules — rejected to
avoid maintenance burden and divergence from upstream.
- Writing a custom React-only skill — rejected as the Vercel skill
already covers the React patterns comprehensively.

Links to places where the discussion took place:
- Source: https://github.com/vercel-labs/agent-skills

### Breaking changes

None

### Special notes for your reviewer

- The skill is installed in
`.agents/skills/vercel-react-best-practices/` as the single source of
truth.
- `.claude/skills/vercel-react-best-practices` is a **directory
symlink** pointing to `.agents/skills/vercel-react-best-practices/`,
following the convention established in #13486. This replaces the
earlier approach of copying SKILL.md into a real directory.
- `public-skills.txt` was updated and `pnpm skills:sync` was run to
update `.gitignore` whitelists.
- Windows compatibility: Windows developers need symlink support enabled
(via `git config core.symlinks true` or Developer Mode). This is
consistent with the project-wide symlink convention adopted in #13486,
and confirmed working by @GeorgeDong32 on Windows 11 — Claude Code CLI
can load skills even when symlinks fall back to plaintext path files.
- The skill contains 60+ markdown rule files covering categories:
rendering, re-renders, bundle optimization, async patterns, server
components, client patterns, and JS performance.
- Rule applicability breakdown for our Electron + React project:

  | Category | Count | Applicable |
  |---|---|---|
  | `js-*` (JS perf) | 13 | Yes |
  | `rerender-*` (React) | 12 | Yes |
  | `rendering-*` | 11 | Mostly |
  | `bundle-*` | 5 | Partially |
  | `client-*` | 4 | Yes |
  | `advanced-*` | 3 | Yes |
  | `async-*` | 4 | Partially |
  | `server-*` (Next.js) | 8 | No |

### Checklist

- [x] PR: The PR description is expressive enough and will help future
contributors
- [x] Code: [Write code that humans can
understand](https://en.wikiquote.org/wiki/Martin_Fowler#code-for-humans)
and [Keep it simple](https://en.wikipedia.org/wiki/KISS_principle)
- [x] Refactor: You have [left the code cleaner than you found it (Boy
Scout
Rule)](https://learning.oreilly.com/library/view/97-things-every/9780596809515/ch08.html)
- [x] Upgrade: Impact of this change on upgrade flows was considered and
addressed if required
- [ ] Documentation: A [user-guide update](https://docs.cherry-ai.com)
was considered and is present (link) or not required. Check this only
when the PR introduces or changes a user-facing feature or behavior.
- [x] Self-review: I have reviewed my own code (e.g., via
[`/gh-pr-review`](/.claude/skills/gh-pr-review/SKILL.md), `gh pr diff`,
or GitHub UI) before requesting review from others

### Release note

```release-note
NONE
```

---------

Signed-off-by: suyao <[email protected]>
Signed-off-by: icarus <[email protected]>
Co-authored-by: Claude Opus 4.6 <[email protected]>
Co-authored-by: icarus <[email protected]>