Add an optional public-website handover after a working preview

A deployment URL does not establish whether the customer's main action and owner handover are ready. This adds a small conditional handover for public customer-facing websites, with a full read-only workflow reference. Existing deployment commands stay unchanged. Private tools and completed decisions skip it; a domain purchase is optional.

Source-only update to skills/deploy-to-vercel/SKILL.md. patch --dry-run --fuzz=0 passes against 063bee94c3f4df8453406c830b0a7df0f2860278. The upstream test suite and model evaluations have not been run.