Document that handoff event_details is Zendesk-only

Other handoff targets return an empty event_details object, as in earlier versions.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: rahulgdsouza

descriptions/0/api.intercom.io.yaml

@@ -38752,11 +38752,11 @@ components:
     standalone_platform_handoff:
       title: Part type - standalone_platform_handoff
       type: object
-      description: Contains the escalation target Fin handed the conversation off to, for conversation part type <code>standalone_platform_handoff</code>.
+      description: Contains the escalation target Fin handed the conversation off to, for conversation part type <code>standalone_platform_handoff</code>. Only present for handoffs to Zendesk; for any other handoff target <code>event_details</code> is an empty object.
       properties:
         handoff:
           type: object
-          description: The escalation Fin attempted.
+          description: The escalation Fin attempted. Omitted when the handoff target is not Zendesk.
           properties:
             type:
               type: string