chore: add server-changes entry for run-queue sweeper stale-entry fix

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: d-cs

.server-changes/run-queue-sweeper-stale-entry.md

@@ -0,0 +1,9 @@
+---
+area: webapp
+type: fix
+---
+
+Concurrency sweeper now removes the message from the worker queue list
+when acking marked runs, eliminating stale `messageKey` tombstones that
+produced "Failed to dequeue message from worker queue" errors when
+consumed by a later BLPOP.