fix(run-engine): sample the combined gauge after batch admission

The dequeue gauge ran before the loop, so a queue's first batch from idle
and its final drain were never sampled with their runs in flight and the
combined chart under-reported. The successful path now re-samples after
admissions; early returns keep the entry sample. Also documents that
combined.current is the declared cap, clamped at admit time.

Author: matt-aitken

internal-packages/run-engine/src/run-queue/index.ts

@@ -5277,6 +5277,10 @@ else
   redis.call('ZADD', masterQueueKey, earliestIdx[2], ckWildcardName)
 end
 
+-- Re-sample the gauge so the emitted snapshot includes this batch's admissions;
+-- the top-of-script sample only covers the early returns where nothing was admitted.
+${QUEUE_METRICS_CK_DEQUEUE_GAUGE_LUA}
+
 return __qmret(results)
       `,
     });

packages/core/src/v3/schemas/queues.ts

@@ -48,7 +48,7 @@ export const QueueItem = z.object({
       /** The combined concurrency cap across all concurrencyKey values of the queue */
       combined: z
         .object({
-          /** The effective/current combined concurrency limit (null = no cap) */
+          /** The current combined concurrency limit as declared or overridden (null = no cap). Enforcement clamps it to the environment concurrency limit at admit time. */
           current: z.number().nullable(),
           /** The declared combined limit an override reverts to on reset */
           base: z.number().nullable(),