[CodFrm]

Checklist / 检查清单

• Fixes mentioned issues / 修复已提及的问题
• Code reviewed by human / 代码通过人工检查
• Changes tested / 已完成测试

N/A — Fixes mentioned issues: there is no issue for this change.

Description / 描述

The scriptcat-userscript Skill now installs with npx skills instead of clone + symlink, and the install can check for updates:

npx skills add scriptscat/scriptcat -g

• skills/scriptcat-userscript/README.md: install now uses npx skills, and updates use npx skills check -g / npx skills update -g. Symlinking is kept for developing the Skill itself.
• example/agent/README.md: the ScriptCat Agent skills repo was renamed from scriptscat/skills to scriptscat/scriptcat-skills, so the link is updated.

This PR changes no runtime code. An earlier revision added a Codex plugin manifest for a separate plugin-marketplace repo. That approach was dropped in favour of npx skills, and the manifest is removed.

Verification

Run with the skills CLI in an isolated HOME:

• npx skills add scriptscat/scriptcat --list finds exactly one skill, scriptcat-userscript. The whole-repo clone took about 40 s.
• npx skills add scriptscat/scriptcat -g -a claude-code -a codex -y installed it. The lock file (~/.agents/.skill-lock.json) records skills/scriptcat-userscript/SKILL.md and a hash of that folder.
• Updates were exercised on sctl (📝 sctl Skill 改为通过 npx skills 安装 sctl#18), which uses the same mechanism. After I changed the recorded hash, npx skills check -g reported an update, and npx skills update -g restored a copy byte-identical to main.
• prettier --check passes on the edited Markdown.

Companion PR: scriptscat/sctl#18.