plugin: support local-based marketplace.json + install endpoint.

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

@@ -826,6 +826,30 @@
           "title": "Skills/config/writeRequest",
           "type": "object"
         },
+        {
+          "properties": {
+            "id": {
+              "$ref": "#/definitions/v2/RequestId"
+            },
+            "method": {
+              "enum": [
+                "plugin/install"
+              ],
+              "title": "Plugin/installRequestMethod",
+              "type": "string"
+            },
+            "params": {
+              "$ref": "#/definitions/v2/PluginInstallParams"
+            }
+          },
+          "required": [
+            "id",
+            "method",
+            "params"
+          ],
+          "title": "Plugin/installRequest",
+          "type": "object"
+        },
         {
           "properties": {
             "id": {
@@ -10897,6 +10921,34 @@
         ],
         "type": "string"
       },
+      "PluginInstallParams": {
+        "$schema": "http://json-schema.org/draft-07/schema#",
+        "properties": {
+          "cwd": {
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "marketplaceName": {
+            "type": "string"
+          },
+          "pluginName": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "marketplaceName",
+          "pluginName"
+        ],
+        "title": "PluginInstallParams",
+        "type": "object"
+      },
+      "PluginInstallResponse": {
+        "$schema": "http://json-schema.org/draft-07/schema#",
+        "title": "PluginInstallResponse",
+        "type": "object"
+      },
       "ProductSurface": {
         "enum": [
           "chatgpt",