0303 — The metrics snapshot is the single source for both the debug readout and the OTel instruments

Context. Two consumers of “current queue state” shipped at once: a human-readable debug readout (String(), scoped per (group, topic)) and the OTel instruments. Two independent implementations of the same numbers would drift apart.

Decision. One snapshot struct/method merges the queue-state query’s DB-truth numbers with the in-process AbandonedRoutines counters; the debug readout and every OTel instrument read from that snapshot, and neither computes its own numbers.

Consequences. The readout is guaranteed to show exactly the data the instruments export to machines — it is the free human-readable consumer of the identical snapshot. Any new health number is added once, in the snapshot, and appears on both surfaces.