feat(app-server): add ThreadItem::DynamicToolCall (#12732)

Previously, clients would call `thread/start` with dynamic_tools set,
and when a model invokes a dynamic tool, it would just make the
server->client `item/tool/call` request and wait for the client's
response to complete the tool call. This works, but it doesn't have an
`item/started` or `item/completed` event.

Now we are doing this:
- [new] emit `item/started` with `DynamicToolCall` populated with the
call arguments
- send an `item/tool/call` server request
- [new] once the client responds, emit `item/completed` with
`DynamicToolCall` populated with the response.

Also, with `persistExtendedHistory: true`, dynamic tool calls are now
reconstructable in `thread/read` and `thread/resume` as
`ThreadItem::DynamicToolCall`.

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json

@@ -1640,50 +1640,6 @@
       ],
       "type": "object"
     },
-    "DynamicToolCallOutputContentItem": {
-      "oneOf": [
-        {
-          "properties": {
-            "text": {
-              "type": "string"
-            },
-            "type": {
-              "enum": [
-                "inputText"
-              ],
-              "title": "InputTextDynamicToolCallOutputContentItemType",
-              "type": "string"
-            }
-          },
-          "required": [
-            "text",
-            "type"
-          ],
-          "title": "InputTextDynamicToolCallOutputContentItem",
-          "type": "object"
-        },
-        {
-          "properties": {
-            "imageUrl": {
-              "type": "string"
-            },
-            "type": {
-              "enum": [
-                "inputImage"
-              ],
-              "title": "InputImageDynamicToolCallOutputContentItemType",
-              "type": "string"
-            }
-          },
-          "required": [
-            "imageUrl",
-            "type"
-          ],
-          "title": "InputImageDynamicToolCallOutputContentItem",
-          "type": "object"
-        }
-      ]
-    },
     "DynamicToolCallParams": {
       "$schema": "http://json-schema.org/draft-07/schema#",
       "properties": {
@@ -1716,7 +1672,7 @@
       "properties": {
         "contentItems": {
           "items": {
-            "$ref": "#/definitions/DynamicToolCallOutputContentItem"
+            "$ref": "#/definitions/v2/DynamicToolCallOutputContentItem"
           },
           "type": "array"
         },
@@ -3008,6 +2964,70 @@
           "title": "DynamicToolCallRequestEventMsg",
           "type": "object"
         },
+        {
+          "properties": {
+            "arguments": {
+              "description": "Dynamic tool call arguments."
+            },
+            "call_id": {
+              "description": "Identifier for the corresponding DynamicToolCallRequest.",
+              "type": "string"
+            },
+            "content_items": {
+              "description": "Dynamic tool response content items.",
+              "items": {
+                "$ref": "#/definitions/v2/DynamicToolCallOutputContentItem"
+              },
+              "type": "array"
+            },
+            "duration": {
+              "allOf": [
+                {
+                  "$ref": "#/definitions/Duration"
+                }
+              ],
+              "description": "The duration of the dynamic tool call."
+            },
+            "error": {
+              "description": "Optional error text when the tool call failed before producing a response.",
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "success": {
+              "description": "Whether the tool call succeeded.",
+              "type": "boolean"
+            },
+            "tool": {
+              "description": "Dynamic tool name.",
+              "type": "string"
+            },
+            "turn_id": {
+              "description": "Turn ID that this dynamic tool call belongs to.",
+              "type": "string"
+            },
+            "type": {
+              "enum": [
+                "dynamic_tool_call_response"
+              ],
+              "title": "DynamicToolCallResponseEventMsgType",
+              "type": "string"
+            }
+          },
+          "required": [
+            "arguments",
+            "call_id",
+            "content_items",
+            "duration",
+            "success",
+            "tool",
+            "turn_id",
+            "type"
+          ],
+          "title": "DynamicToolCallResponseEventMsg",
+          "type": "object"
+        },
         {
           "properties": {
             "item_id": {
@@ -9094,6 +9114,58 @@
         "title": "DeprecationNoticeNotification",
         "type": "object"
       },
+      "DynamicToolCallOutputContentItem": {
+        "oneOf": [
+          {
+            "properties": {
+              "text": {
+                "type": "string"
+              },
+              "type": {
+                "enum": [
+                  "inputText"
+                ],
+                "title": "InputTextDynamicToolCallOutputContentItemType",
+                "type": "string"
+              }
+            },
+            "required": [
+              "text",
+              "type"
+            ],
+            "title": "InputTextDynamicToolCallOutputContentItem",
+            "type": "object"
+          },
+          {
+            "properties": {
+              "imageUrl": {
+                "type": "string"
+              },
+              "type": {
+                "enum": [
+                  "inputImage"
+                ],
+                "title": "InputImageDynamicToolCallOutputContentItemType",
+                "type": "string"
+              }
+            },
+            "required": [
+              "imageUrl",
+              "type"
+            ],
+            "title": "InputImageDynamicToolCallOutputContentItem",
+            "type": "object"
+          }
+        ]
+      },
+      "DynamicToolCallStatus": {
+        "enum": [
+          "inProgress",
+          "completed",
+          "failed"
+        ],
+        "type": "string"
+      },
       "DynamicToolSpec": {
         "properties": {
           "description": {
@@ -12895,6 +12967,59 @@
             "title": "McpToolCallThreadItem",
             "type": "object"
           },
+          {
+            "properties": {
+              "arguments": true,
+              "contentItems": {
+                "items": {
+                  "$ref": "#/definitions/v2/DynamicToolCallOutputContentItem"
+                },
+                "type": [
+                  "array",
+                  "null"
+                ]
+              },
+              "durationMs": {
+                "description": "The duration of the dynamic tool call in milliseconds.",
+                "format": "int64",
+                "type": [
+                  "integer",
+                  "null"
+                ]
+              },
+              "id": {
+                "type": "string"
+              },
+              "status": {
+                "$ref": "#/definitions/v2/DynamicToolCallStatus"
+              },
+              "success": {
+                "type": [
+                  "boolean",
+                  "null"
+                ]
+              },
+              "tool": {
+                "type": "string"
+              },
+              "type": {
+                "enum": [
+                  "dynamicToolCall"
+                ],
+                "title": "DynamicToolCallThreadItemType",
+                "type": "string"
+              }
+            },
+            "required": [
+              "arguments",
+              "id",
+              "status",
+              "tool",
+              "type"
+            ],
+            "title": "DynamicToolCallThreadItem",
+            "type": "object"
+          },
           {
             "properties": {
               "agentsStates": {