Add skill package support and modern-web sample

[Copilot]

Implements the built-in skill package subsystem for the sh1pt CLI (skills list / retrieve / install) and ships the modern-web guidance pack as the first entry in the local registry.

Skills infrastructure (already landed in #423, included here for completeness)

• loadBuiltinSkills() scans packages/cli/skills/ for sh1pt.skill.json manifests and loads guide content
• skills list / search / info / retrieve / install / new / publish / marketplaces commands wired into the CLI
• Managed-block install: appends or idempotently updates a <!-- sh1pt-skill:<name> start/end --> fence in target files (AGENTS.md, CLAUDE.md, .github/copilot-instructions.md, .cursor/rules/, etc.)

modern-web skill pack

• Expanded guide (skills/modern-web/guides/modern-web.md) from a stub to 8 structured sections: code changes, TypeScript/JS, framework usage, testing, security, performance, accessibility, CI/GitHub Actions, documentation
• Example install output:

  <!-- sh1pt-skill:modern-web start -->
  ## sh1pt skill: Modern Web Guidance
  _Installed from profullstack/modern-web@0.1.0 · trust: verified_
  …
  <!-- sh1pt-skill:modern-web end -->
  

Registry index

• Added skills/registry.json as the explicit local registry listing all built-in skills with name, version, title, trustLevel, and supported targets — serves as the canonical source for tooling that needs to enumerate skills without scanning the filesystem

[github-actions]

vu1nz Security Review

0 finding(s) in PR #?

No security issues found.