support plugin/list. (#13540)

Introduce a plugin/list which reads from local marketplace.json.
Also update the signature for plugin/install.

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

@@ -1,21 +1,21 @@
 {
   "$schema": "http://json-schema.org/draft-07/schema#",
-  "properties": {
-    "cwd": {
-      "type": [
-        "string",
-        "null"
-      ]
-    },
-    "marketplaceName": {
+  "definitions": {
+    "AbsolutePathBuf": {
+      "description": "A path that is guaranteed to be absolute and normalized (though it is not guaranteed to be canonicalized or exist on the filesystem).\n\nIMPORTANT: When deserializing an `AbsolutePathBuf`, a base path must be set using [AbsolutePathBufGuard::new]. If no base path is set, the deserialization will fail unless the path being deserialized is already absolute.",
       "type": "string"
+    }
+  },
+  "properties": {
+    "marketplacePath": {
+      "$ref": "#/definitions/AbsolutePathBuf"
     },
     "pluginName": {
       "type": "string"
     }
   },
   "required": [
-    "marketplaceName",
+    "marketplacePath",
     "pluginName"
   ],
   "title": "PluginInstallParams",