feat(responses): add output_text delta events to responses

docs/_static/llama-stack-spec.yaml

@@ -5294,11 +5294,13 @@ components:
     OpenAIResponseObjectStream:
       oneOf:
         - $ref: '#/components/schemas/OpenAIResponseObjectStreamResponseCreated'
+        - $ref: '#/components/schemas/OpenAIResponseObjectStreamResponseOutputTextDelta'
         - $ref: '#/components/schemas/OpenAIResponseObjectStreamResponseCompleted'
       discriminator:
         propertyName: type
         mapping:
           response.created: '#/components/schemas/OpenAIResponseObjectStreamResponseCreated'
+          response.output_text.delta: '#/components/schemas/OpenAIResponseObjectStreamResponseOutputTextDelta'
           response.completed: '#/components/schemas/OpenAIResponseObjectStreamResponseCompleted'
     "OpenAIResponseObjectStreamResponseCompleted":
       type: object
@@ -5330,6 +5332,33 @@ components:
         - type
       title: >-
         OpenAIResponseObjectStreamResponseCreated
+    "OpenAIResponseObjectStreamResponseOutputTextDelta":
+      type: object
+      properties:
+        content_index:
+          type: integer
+        delta:
+          type: string
+        item_id:
+          type: string
+        output_index:
+          type: integer
+        sequence_number:
+          type: integer
+        type:
+          type: string
+          const: response.output_text.delta
+          default: response.output_text.delta
+      additionalProperties: false
+      required:
+        - content_index
+        - delta
+        - item_id
+        - output_index
+        - sequence_number
+        - type
+      title: >-
+        OpenAIResponseObjectStreamResponseOutputTextDelta
     CreateUploadSessionRequest:
       type: object
       properties: