feat(skills): separate standard docs from user experience

[NWYLZW]

Summary

• Keep the Docs Skill authoritative for standard documentation and route experience to Q&A.
• Align layered startup prompts with bundled guidance and keep long URLs on their own line.
• Add version and assistant metadata for the canonical Docs Skill snapshot.

Validation

• Skill structure validator passed.
• Coordinated local/cross-repository links and anchors checked (204 links).
• Scoped formatting and diff checks passed.
• Markdown-only navigation changes; no browser/native claims.