feat: Add plugin share access controls (#21124)

Extends `plugin/share/save` to accept optional discoverability and
shareTargets while uploading plugin contents, and adds
`plugin/share/updateTargets` for share-only target updates without
re-uploading.

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.v2.schemas.json

@@ -1569,6 +1569,30 @@
           "title": "Plugin/share/saveRequest",
           "type": "object"
         },
+        {
+          "properties": {
+            "id": {
+              "$ref": "#/definitions/RequestId"
+            },
+            "method": {
+              "enum": [
+                "plugin/share/updateTargets"
+              ],
+              "title": "Plugin/share/updateTargetsRequestMethod",
+              "type": "string"
+            },
+            "params": {
+              "$ref": "#/definitions/PluginShareUpdateTargetsParams"
+            }
+          },
+          "required": [
+            "id",
+            "method",
+            "params"
+          ],
+          "title": "Plugin/share/updateTargetsRequest",
+          "type": "object"
+        },
         {
           "properties": {
             "id": {
@@ -9090,6 +9114,14 @@
       "title": "PluginShareDeleteResponse",
       "type": "object"
     },
+    "PluginShareDiscoverability": {
+      "enum": [
+        "LISTED",
+        "UNLISTED",
+        "PRIVATE"
+      ],
+      "type": "string"
+    },
     "PluginShareListItem": {
       "properties": {
         "localPluginPath": {
@@ -9136,9 +9168,46 @@
       "title": "PluginShareListResponse",
       "type": "object"
     },
+    "PluginSharePrincipal": {
+      "properties": {
+        "name": {
+          "type": "string"
+        },
+        "principalId": {
+          "type": "string"
+        },
+        "principalType": {
+          "$ref": "#/definitions/PluginSharePrincipalType"
+        }
+      },
+      "required": [
+        "name",
+        "principalId",
+        "principalType"
+      ],
+      "type": "object"
+    },
+    "PluginSharePrincipalType": {
+      "enum": [
+        "user",
+        "group",
+        "workspace"
+      ],
+      "type": "string"
+    },
     "PluginShareSaveParams": {
       "$schema": "http://json-schema.org/draft-07/schema#",
       "properties": {
+        "discoverability": {
+          "anyOf": [
+            {
+              "$ref": "#/definitions/PluginShareDiscoverability"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        },
         "pluginPath": {
           "$ref": "#/definitions/AbsolutePathBuf"
         },
@@ -9147,6 +9216,15 @@
             "string",
             "null"
           ]
+        },
+        "shareTargets": {
+          "items": {
+            "$ref": "#/definitions/PluginShareTarget"
+          },
+          "type": [
+            "array",
+            "null"
+          ]
         }
       },
       "required": [
@@ -9172,6 +9250,57 @@
       "title": "PluginShareSaveResponse",
       "type": "object"
     },
+    "PluginShareTarget": {
+      "properties": {
+        "principalId": {
+          "type": "string"
+        },
+        "principalType": {
+          "$ref": "#/definitions/PluginSharePrincipalType"
+        }
+      },
+      "required": [
+        "principalId",
+        "principalType"
+      ],
+      "type": "object"
+    },
+    "PluginShareUpdateTargetsParams": {
+      "$schema": "http://json-schema.org/draft-07/schema#",
+      "properties": {
+        "remotePluginId": {
+          "type": "string"
+        },
+        "shareTargets": {
+          "items": {
+            "$ref": "#/definitions/PluginShareTarget"
+          },
+          "type": "array"
+        }
+      },
+      "required": [
+        "remotePluginId",
+        "shareTargets"
+      ],
+      "title": "PluginShareUpdateTargetsParams",
+      "type": "object"
+    },
+    "PluginShareUpdateTargetsResponse": {
+      "$schema": "http://json-schema.org/draft-07/schema#",
+      "properties": {
+        "principals": {
+          "items": {
+            "$ref": "#/definitions/PluginSharePrincipal"
+          },
+          "type": "array"
+        }
+      },
+      "required": [
+        "principals"
+      ],
+      "title": "PluginShareUpdateTargetsResponse",
+      "type": "object"
+    },
     "PluginSkillReadParams": {
       "$schema": "http://json-schema.org/draft-07/schema#",
       "properties": {