feat: add recent_chunks to feedback endpoint for diagnostics (#9594)

* feat: add recent_chunks field to feedback endpoint

Accept an optional recent_chunks string in the /v1/metadata/feedback
POST body and forward it to PostHog. Contains the last 100 truncated
streaming chunks as JSON for debugging issues reported via /feedback.

🐾 Generated with [Letta Code](https://letta.com)

Co-Authored-By: Letta <noreply@letta.com>

* chore: regenerate openapi specs with recent_chunks field

---------

Co-authored-by: Letta <noreply@letta.com>

fern/openapi.json

@@ -21696,6 +21696,13 @@
                   },
                   "billing_tier": {
                     "type": "string"
+                  },
+                  "recent_chunks": {
+                    "type": "array",
+                    "items": {
+                      "type": "object",
+                      "additionalProperties": {}
+                    }
                   }
                 },
                 "required": ["message"]