Add maintained Vercel REST connection

[zackbart]

Summary

• add a dependency-free Vercel REST provider with 18 named tools and split GET, mutation, and upload hatches
• keep environment values write-only in named tools, confine arbitrary paths, and bound response, pagination, build-log, and runtime-log reads
• add package export, provider guide, audit record, live OpenAPI drift manifest, registry coverage, and 0.22.1 release metadata

Independent review

Claude Opus 5 reviewed the complete diff. The implementation incorporates its concrete findings: Vercel env-create envelope handling, raw output envelopes, runtime stream bounds, upload-header refusal, and changelog placement.

Verification

• npm run release:check
• npm run drift:check -- --specs
• 120 test suites; 2,897 passed, 40 skipped
• npm audit: 0 vulnerabilities
• package smoke: passed; Docker-only generated-container branch skipped because Docker is unavailable locally