Adds scripts/verify-fast.mjs + root `pnpm verify:fast`, an opt-in, flake-free
verification path that runs typecheck + build scoped to the changed packages
(reusing test-changed.mjs git-diff / changed-package resolution) plus the
existing boot smoke once, with no test suite. Each step is bounded by the
shared runWithWatchdog (class "changed"); exits nonzero on the first failure.
No default changed: pnpm test, the merge gate, and CI are untouched.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>