chore: combine the two snapshots-since server-changes notes into one entry

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: d-cs

.server-changes/snapshots-since-replica-primary-fallback.md

@@ -3,4 +3,4 @@ area: webapp
 type: improvement
 ---
 
-Run snapshot polling no longer errors or pays extra latency when the database read replica hasn't yet replicated the snapshot the runner is polling from (`RUN_ENGINE_READ_REPLICA_SNAPSHOTS_SINCE_ENABLED`): the read is briefly retried on the replica and served from the primary if it still hasn't caught up.
+Run snapshot polling no longer errors or pays extra latency when the database read replica hasn't yet replicated the snapshot the runner is polling from (`RUN_ENGINE_READ_REPLICA_SNAPSHOTS_SINCE_ENABLED`): the read is briefly retried on the replica and served from the primary if it still hasn't caught up. Polling also now rejects a since-snapshot id that doesn't belong to the run being polled.