[skills] Sync marketplace with current docs

[vercel-gh-bot-2]

• Stale claim: vercel integration categories / vercel integration discover are "(read-only, no auth)" and "Steps 1–2 need no auth". Correction: they are read-only but need a Vercel login (no provider account). Source: the CLI prompts for credentials before any command not in subcommandsWithoutToken (login, logout, help, init, build, changelog, deploy, sandbox, telemetry, upgrade, version, skills, agent, whoami). integration is not on that list (vercel/vercel packages/cli/src/index.ts L666–720), and categories calls the authenticated client.fetch('/v2/integrations/categories'). Docs: https://vercel.com/kb/guide/using-coding-agents-to-procure-vercel-marketplace-integrations (last_updated 2026-06-17) has "Step 2: Log in" before discovery: "Once you authenticate, both you and your agent have access to all Marketplace integrations. No need to authenticate separately with each provider."

Verification

run_plugin_checks: build, typecheck, validate, and test all passed (1079 pass, 0 fail).

Test updates

None.

Not changed

• The category map slugs (searching, support-agent, web-automation, …) come from the live /v2/integrations/categories API. No docs page lists them, so I could not check them.
• Every other CLI subcommand, flag, and alias in the skill matches https://vercel.com/docs/cli/integration (last_updated 2026-09-17): add --no-claim, accept-terms (interactive only), installations, resource claim, guide --framework, and vercel install / vercel i. The provider skill install and the npx skills add recovery hint match packages/cli/src/commands/integration/add-auto-provision.ts.

Opened automatically by the vercel-plugin drift agent. Review before merge.