Push: a failed push-retired.json write keeps a retired subscription registered #2013

Found while answering a CodeRabbit thread on #1995.

In server/push.ts deliver(), a push answered 404/410 writes push-retired.json first and only then removes the subscription:

writeJsonPrivate(retiredPath, ...);          // main: server/push.ts:354
const next = without((endpoint) => endpoint === subscription.endpoint);
if (next) persist(next);

If that write fails (a full disk, a read-only state dir), it throws, the subscription stays registered, and the next push goes to the dead endpoint again. push-retired.json is telemetry (its own comment says so), so its write should not decide whether a retired subscription is removed. Expected: the subscription is removed and the mark kept in memory even when the file cannot be written.

This is on main as well; #1995 keeps the same order (it only made the delivery-record write and the retired list's expiry rewrite non-throwing).