Rudder's setup ran before Vite and the sign-in proxy, so the whole site answered 502 for minutes on every
start while the engine built and ~742 MB downloaded; on the first start the download was reset mid-file and
Rudder stayed offline. Now the runtime and pinned model are baked into an early image layer (SHA-256
checked, resumed and retried on a stall), setup runs in the background, /api/rudder answers "starting"
meanwhile, and the dev server restarts once when setup ends so the engine starts.
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