Refactor verifier UX into unified CommandLayer visual system

[GsCommand]

Goal

Refactor public/verify.html so the verifier feels like part of the same protocol platform as the homepage and Capabilities page.

Scope

• Preserve all existing verification behavior and API calls.
• Preserve proof verification states and logic.
• Keep the dark verifier panel aesthetic where helpful, but unify nav, spacing, typography, and CTA language with the rest of the site.

Required updates

• Use standard top nav:
  • Home
  • Capabilities
  • Verifier
  • SDK
  • Docs
  • GitHub
• Add clearer verification flow sections:
  • Paste receipt
  • Verification checks
  • VERIFIED / INVALID result
  • Proof URL section
• Add a section linking back to capabilities:
  • This verifier checks CommandLayer capability receipts.
• Add a simple "What gets checked" explainer:
  • schema
  • canonicalization
  • hash
  • signature
  • signer identity

Constraints

• Do not change verifier API behavior.
• Do not change receipt validation semantics.
• Avoid major JS rewrites.

Acceptance checks

• Existing verification flow still works.
• Nav is consistent with Capabilities-first structure.
• Verifier visually feels like part of the same platform.
• Mobile layout remains usable.