fix(ci): allow doc freshness workflow to update AGENTS.md (#452)

Author: Copilot

.github/workflows/doc-freshness-check.lock.yml

@@ -14,6 +14,8 @@ network:
 safe-outputs:
   create-pull-request:
     max: 1
+    allowed-files:
+      - AGENTS.md
 ---
 
 # Documentation Freshness Check