Feat: cxa-1833 update model/list (#12958)

### Summary
Update `model/list` in app server to include more upgrade information.

codex-rs/app-server-protocol/schema/json/v2/ModelListResponse.json

@@ -68,6 +68,16 @@
             "string",
             "null"
           ]
+        },
+        "upgradeInfo": {
+          "anyOf": [
+            {
+              "$ref": "#/definitions/ModelUpgradeInfo"
+            },
+            {
+              "type": "null"
+            }
+          ]
         }
       },
       "required": [
@@ -82,6 +92,35 @@
       ],
       "type": "object"
     },
+    "ModelUpgradeInfo": {
+      "properties": {
+        "migrationMarkdown": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "model": {
+          "type": "string"
+        },
+        "modelLink": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "upgradeCopy": {
+          "type": [
+            "string",
+            "null"
+          ]
+        }
+      },
+      "required": [
+        "model"
+      ],
+      "type": "object"
+    },
     "ReasoningEffort": {
       "description": "See https://platform.openai.com/docs/guides/reasoning?api-mode=responses#get-started-with-reasoning",
       "enum": [