PR #30136 review caught that website/docs/user-guide/docker.md still
said "The dashboard side-process is **not supervised** — if it
crashes, it stays down until the container restarts." That was true
under tini but is the opposite of the s6 behavior this PR ships and
`test_dashboard_restarts_after_crash` proves.
Replace with a description of what users actually see now: automatic
restart by s6-overlay, new PID after a short backoff, logs via
`docker logs`. The standalone-container caveat carries forward
unchanged.
04d1894f36