feat: Expose plugin share metadata in shareContext (#21495)

Extends PluginSummary.shareContext with shareUrl and reader shareTargets

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

@@ -8798,6 +8798,21 @@
         },
         "remotePluginId": {
           "type": "string"
+        },
+        "shareTargets": {
+          "items": {
+            "$ref": "#/definitions/PluginSharePrincipal"
+          },
+          "type": [
+            "array",
+            "null"
+          ]
+        },
+        "shareUrl": {
+          "type": [
+            "string",
+            "null"
+          ]
         }
       },
       "required": [