fix: Restore previous responses to input list, not messages

This adjusts the restoration of previous responses to prepend them to
the list of Responses API inputs instead of our converted list of Chat
Completion messages. This matches the expected behavior of the
Responses API, and I misinterpreted the nuances here in the initial implementation.

Signed-off-by: Ben Browning <bbrownin@redhat.com>

docs/_static/llama-stack-spec.yaml

@@ -4534,34 +4534,10 @@ components:
         - event_type
         - turn_id
       title: AgentTurnResponseTurnStartPayload
-    OpenAIResponseInputMessage:
-      type: object
-      properties:
-        content:
-          oneOf:
-            - type: string
-            - type: array
-              items:
-                $ref: '#/components/schemas/OpenAIResponseInputMessageContent'
-        role:
-          oneOf:
-            - type: string
-              const: system
-            - type: string
-              const: developer
-            - type: string
-              const: user
-            - type: string
-              const: assistant
-        type:
-          type: string
-          const: message
-          default: message
-      additionalProperties: false
-      required:
-        - content
-        - role
-      title: OpenAIResponseInputMessage
+    OpenAIResponseInput:
+      oneOf:
+        - $ref: '#/components/schemas/OpenAIResponseOutputMessageWebSearchToolCall'
+        - $ref: '#/components/schemas/OpenAIResponseMessage'
     OpenAIResponseInputMessageContent:
       oneOf:
         - $ref: '#/components/schemas/OpenAIResponseInputMessageContentText'
@@ -4625,6 +4601,79 @@ components:
       required:
         - type
       title: OpenAIResponseInputToolWebSearch
+    OpenAIResponseMessage:
+      type: object
+      properties:
+        content:
+          oneOf:
+            - type: string
+            - type: array
+              items:
+                $ref: '#/components/schemas/OpenAIResponseInputMessageContent'
+            - type: array
+              items:
+                $ref: '#/components/schemas/OpenAIResponseOutputMessageContent'
+        role:
+          oneOf:
+            - type: string
+              const: system
+            - type: string
+              const: developer
+            - type: string
+              const: user
+            - type: string
+              const: assistant
+        type:
+          type: string
+          const: message
+          default: message
+        id:
+          type: string
+        status:
+          type: string
+      additionalProperties: false
+      required:
+        - content
+        - role
+        - type
+      title: OpenAIResponseMessage
+      description: >-
+        Corresponds to the various Message types in the Responses API. They are all
+        under one type because the Responses API gives them all the same "type" value,
+        and there is no way to tell them apart in certain scenarios.
+    OpenAIResponseOutputMessageContent:
+      type: object
+      properties:
+        text:
+          type: string
+        type:
+          type: string
+          const: output_text
+          default: output_text
+      additionalProperties: false
+      required:
+        - text
+        - type
+      title: >-
+        OpenAIResponseOutputMessageContentOutputText
+    "OpenAIResponseOutputMessageWebSearchToolCall":
+      type: object
+      properties:
+        id:
+          type: string
+        status:
+          type: string
+        type:
+          type: string
+          const: web_search_call
+          default: web_search_call
+      additionalProperties: false
+      required:
+        - id
+        - status
+        - type
+      title: >-
+        OpenAIResponseOutputMessageWebSearchToolCall
     CreateOpenaiResponseRequest:
       type: object
       properties:
@@ -4633,7 +4682,7 @@ components:
             - type: string
             - type: array
               items:
-                $ref: '#/components/schemas/OpenAIResponseInputMessage'
+                $ref: '#/components/schemas/OpenAIResponseInput'
           description: Input message(s) to create the response.
         model:
           type: string
@@ -4717,73 +4766,13 @@ components:
       title: OpenAIResponseObject
     OpenAIResponseOutput:
       oneOf:
-        - $ref: '#/components/schemas/OpenAIResponseOutputMessage'
+        - $ref: '#/components/schemas/OpenAIResponseMessage'
         - $ref: '#/components/schemas/OpenAIResponseOutputMessageWebSearchToolCall'
       discriminator:
         propertyName: type
         mapping:
-          message: '#/components/schemas/OpenAIResponseOutputMessage'
+          message: '#/components/schemas/OpenAIResponseMessage'
           web_search_call: '#/components/schemas/OpenAIResponseOutputMessageWebSearchToolCall'
-    OpenAIResponseOutputMessage:
-      type: object
-      properties:
-        id:
-          type: string
-        content:
-          type: array
-          items:
-            $ref: '#/components/schemas/OpenAIResponseOutputMessageContent'
-        role:
-          type: string
-          const: assistant
-          default: assistant
-        status:
-          type: string
-        type:
-          type: string
-          const: message
-          default: message
-      additionalProperties: false
-      required:
-        - id
-        - content
-        - role
-        - status
-        - type
-      title: OpenAIResponseOutputMessage
-    OpenAIResponseOutputMessageContent:
-      type: object
-      properties:
-        text:
-          type: string
-        type:
-          type: string
-          const: output_text
-          default: output_text
-      additionalProperties: false
-      required:
-        - text
-        - type
-      title: >-
-        OpenAIResponseOutputMessageContentOutputText
-    "OpenAIResponseOutputMessageWebSearchToolCall":
-      type: object
-      properties:
-        id:
-          type: string
-        status:
-          type: string
-        type:
-          type: string
-          const: web_search_call
-          default: web_search_call
-      additionalProperties: false
-      required:
-        - id
-        - status
-        - type
-      title: >-
-        OpenAIResponseOutputMessageWebSearchToolCall
     OpenAIResponseObjectStream:
       oneOf:
         - $ref: '#/components/schemas/OpenAIResponseObjectStreamResponseCreated'