Put Vale in the pipeline

When to use this

Vale runs locally and should now run automatically.

Prerequisites

1. vale ls-config resolves, and a plain vale <path> run works locally. Do not wire up CI for a config that does not resolve — the failure will look like a CI problem.
2. The user has said whether the job should block. Ask if not.

Advisory or blocking

Only error sets a non-zero exit code. Warnings and suggestions exit 0, so a job wired up naively passes no matter how much it reports.