Move `npm run build` out of the Docker image onto the runner, where actions/cache persists .next/cache across runs (the in-Docker build discarded it every time). The image now just packages the prebuilt .next and serves it with `next start`; runtime and the DocSearch entrypoint injection are unchanged.
Also: checkout full history (fetch-depth: 0) so per-page dates are correct, guard buildGitDateMap against shallow clones (correct-or-absent, never wrong), modernise the Docker actions (build-push-action v6, provenance: false), and add a path-filtered pull_request trigger so pipeline changes are validated before merge.
Smoke-tested via isolated build + docker run: serves /, /introduction, /api, sitemap, static assets (200); DocSearch placeholder injection intact.
Replace ~314 `git log` spawns per gen script with a single `git log --name-only` pass, memoised per process. Cuts gen:last-updated + gen:sitemap from ~15s to ~1.5s.
Output is byte-identical to the per-file version; still degrades to no-dates when git is unavailable (e.g. the Docker image).
