fix(discord): use partial mock for @buape/carbon in slash test

Replace the full manual mock with importOriginal spread so new SDK
exports are available automatically. Only ChannelType, MessageType,
and Client are overridden — the rest come from the real module.

Prevents CI breakage when @buape/carbon adds exports (e.g. the
recent StringSelectMenu failure that blocked unrelated PRs).

Closes #13244

src/discord/monitor.slash.test.ts

@@ -3,24 +3,19 @@ import { createReplyDispatcherWithTyping } from "../auto-reply/reply/reply-dispa
 
 const dispatchMock = vi.fn();
 
-vi.mock("@buape/carbon", () => ({
-  ChannelType: { DM: "dm", GroupDM: "group" },
-  MessageType: {
-    ChatInputCommand: 1,
-    ContextMenuCommand: 2,
-    Default: 0,
-  },
-  Button: class {},
-  Command: class {},
-  Client: class {},
-  MessageCreateListener: class {},
-  MessageReactionAddListener: class {},
-  MessageReactionRemoveListener: class {},
-  PresenceUpdateListener: class {},
-  Row: class {},
-  StringSelectMenu: class {},
-  BaseMessageInteractiveComponent: class {},
-}));
+vi.mock("@buape/carbon", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("@buape/carbon")>();
+  return {
+    ...actual,
+    ChannelType: { DM: "dm", GroupDM: "group" },
+    MessageType: {
+      ChatInputCommand: 1,
+      ContextMenuCommand: 2,
+      Default: 0,
+    },
+    Client: class {},
+  };
+});
 
 vi.mock("../auto-reply/dispatch.js", async (importOriginal) => {
   const actual = await importOriginal<typeof import("../auto-reply/dispatch.js")>();