Project-local vercel lookup hardened; API rewritten async

Major Changes

• 3f21605: Improve project-local vercel binary lookup fidelity by resolving only through the local vercel package, stopping lookup at project boundaries, and skipping directories that have unsafe ownership or access mode. Major bump, because findVercelCli has been made async and clearVercelCliCache renamed to clearVercelCliLookupCache. It is also substantially a complete rewrite.