fix(gateway): adminListChannels 按平台聚合——bare+kook多个adapter不再拆成多行导致重复账号

- 根因: caps循环把 kook(bare)+kook:fc2048(多账号) 分别append, 每行Accounts都是完整platform账号集→前端显示两个kook且fc2048重复(主人'只点一次创建出两个kook')
- 修: 按platform聚合(hasChannelSummary检查), 同platform只一行(Name=platform), Accounts为整个platform账号集; 保留agent-121删除同步(平台有账号才显示)
- 测试断言: kook:3fc8/conf0 → kook(聚合行) 更新
- 全仓 go build/vet/test绿; 前端无涉

internal/services/gateway/extra_test.go

@@ -597,8 +597,8 @@ func TestAdminChannels_SurfacesBotIdentity(t *testing.T) {
 	if err := json.Unmarshal(decodeBody(t, body)["data"], &items); err != nil {
 		t.Fatalf("decode: %v", err)
 	}
-	if len(items) != 1 || items[0].Name != "kook:conf0" {
-		t.Fatalf("items = %+v, want single kook:conf0", items)
+	if len(items) != 1 || items[0].Name != "kook" {
+		t.Fatalf("items = %+v, want single kook row", items)
 	}
 	if len(items[0].Accounts) != 1 {
 		t.Fatalf("accounts = %+v, want one", items[0].Accounts)