Make item event responses compatible with strict schemas

internal/modules/dnd/extract/itemevents/assets/schemas/dnd_item_events_llm.v1.json

@@ -10,13 +10,13 @@
       "items": {
         "type": "object",
         "additionalProperties": false,
-        "required": ["name", "kind", "source_refs"],
+        "required": ["name", "kind", "quantity", "from", "to", "source_refs"],
         "properties": {
           "name": {"type": "string"},
           "kind": {"type": "string"},
-          "quantity": {"type": "integer"},
-          "from": {"type": "string"},
-          "to": {"type": "string"},
+          "quantity": {"type": ["integer", "null"]},
+          "from": {"type": ["string", "null"]},
+          "to": {"type": ["string", "null"]},
           "source_refs": {
             "type": "array",
             "items": {