Extends the same dynamic-runner gate ci.yml already uses (build/test-unit/test-vitest)
to quality.yml's fast-gates/fast-vitest/fast-unit — the ~9min-on-ubuntu jobs that run on
every PR→release/**. Inert until USE_VPS_RUNNER flips to true (falls back to ubuntu-latest
when the var is unset/false OR the PR is a fork — own-origin branches only, never the LAN
runner for fork code). lint-guard/merge-integrity stay on ubuntu-latest (trivial; keeps VPS
concurrency low). No behavior change today.