The act_runner cache server is now reachable from job containers: jobs were
landing on isolated per-job docker networks and couldn't reach the runner's
cache server on docker0 (getCacheEntry ETIMEDOUT, ~5 min wasted/build). Fixed
runner-side by putting the runner + all job containers on a shared dedicated
network (`act-cache-net`, runner at 172.30.0.2) and pointing cache.host at it —
verified a container on that network reaches the cache port.
Restores `cache: npm` on Setup Node and the actions/cache node_modules step
(restore + save-on-miss-and-success). Reverts 10270b75 now that the underlying
network issue is resolved.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>