0466 — `__system.job_requests` runs with `DeliveryLogModeAll` so successes leave rows

Context. Derived job-request status needs a positive record that a group ran a request successfully. On the normal delivery path, success leaves no delivery_log row, so “this group succeeded on this request” would be unknowable after the fact.

Decision. The __system.job_requests topic is configured with DeliveryLogModeAll, so successful deliveries also write a delivery_log row, giving the status derivation its success records.

Consequences. One extra row per successful delivery — acceptable here because the topic produces at most one message per job per minute. This stays a per-topic setting: hot topics do not pay it, and their success path keeps writing nothing.