feat(website): add dedicated Registry page with publish/install guide

[luongnv89]

Summary

• Add a Registry nav link to the catalog website (between Docs and Best Practices)
• New #registry page rendered by renderRegistryPage() with 5 sections:
  • Install from the Registry — bare name, scoped name, --no-cache, -p flag examples
  • Publish Your Skill — full pipeline steps + all flags (--dry-run, --force, --yes, --machine)
  • How Resolution Works — commit-pinned install explanation
  • End-to-End Workflow — scaffold → develop → publish → community install
  • Registry Links — quick reference table
• navigateTo() and handleHashChange() updated to handle #registry hash

Test plan

• Navigate to #registry directly via URL hash
• Click "Registry" in the nav bar — page renders correctly
• Copy buttons work on all code blocks
• All links open correctly (registry repo, gh CLI, npm)
• Page is responsive on mobile

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