fix(zalouser): fix group mention detection failures

- Deduplicate mention IDs via Set in extractMentionIds
- Add fallback to getOwnId when fetchAccountInfo shape changes
- Narrow fetchAccountInfo return type to { profile: User }
- Fail closed when requireMention=true but detection unavailable
- Add test for mention-unavailable fail-closed behavior

extensions/zalouser/src/monitor.group-gating.test.ts

@@ -170,6 +170,25 @@ describe("zalouser monitor group mention gating", () => {
     expect(sendTypingZalouserMock).not.toHaveBeenCalled();
   });
 
+  it("fails closed when requireMention=true but mention detection is unavailable", async () => {
+    const { dispatchReplyWithBufferedBlockDispatcher } = installRuntime({
+      commandAuthorized: false,
+    });
+    await __testing.processMessage({
+      message: createGroupMessage({
+        canResolveExplicitMention: false,
+        hasAnyMention: false,
+        wasExplicitlyMentioned: false,
+      }),
+      account: createAccount(),
+      config: createConfig(),
+      runtime: createRuntimeEnv(),
+    });
+
+    expect(dispatchReplyWithBufferedBlockDispatcher).not.toHaveBeenCalled();
+    expect(sendTypingZalouserMock).not.toHaveBeenCalled();
+  });
+
   it("dispatches explicitly-mentioned group messages and marks WasMentioned", async () => {
     const { dispatchReplyWithBufferedBlockDispatcher } = installRuntime({
       commandAuthorized: false,

extensions/zalouser/src/zca-client.ts

@@ -138,7 +138,7 @@ export type API = {
       cookies: unknown[];
     };
   };
-  fetchAccountInfo(): Promise<{ profile: User } | User>;
+  fetchAccountInfo(): Promise<{ profile: User }>;
   getAllFriends(): Promise<User[]>;
   getOwnId(): string;
   getAllGroups(): Promise<{