Deploy Runtype Sandbox

Deploy a session-tier Runtype Sandbox preview. The preview URL is the credential and is bound to the container epoch: a new container mints a new URL, reported by effectivePolicy.freshContainer and previewUrlChanged. Omitted retention preserves unlimited retention; explicit retention is metered and rollout-gated, and the preview is refused from the retention deadline on. sleepPolicy { mode: “never” } keeps the container running until that deadline and requires retention of 10m, 1h or 24h. A redeploy stops the previous server first and fails if the new server never answers on the port.