docs(server-changes): document mollifier trigger-time decisions

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

Author: d-cs

.server-changes/mollifier-trigger.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: feature
+---
+
+Mollifier trigger-time decisions: route `engine.trigger` through the mollifier gate, mollify burst triggers into the Redis buffer, claim idempotency keys before the gate, and serve buffered runs through a trigger-path read fallback.