refactor(workbench): remove unused WorkModeSwitcher — workbench is always focus mode

frontend/src/app/(investor)/companies/[id]/workbench/page.tsx

@@ -7,7 +7,6 @@ import { HealthRadar, DIMENSIONS_14, DIMENSIONS_14_DETAIL, HealthDimensionDetail
 import { LoadingSpinner } from "@/components/shared/LoadingSpinner";
 import { EmptyState } from "@/components/shared/EmptyState";
 import { HighlightsPanel } from "@/components/workbench/HighlightsPanel";
-import { WorkModeSwitcher, type WorkMode } from "@/components/shared/WorkModeSwitcher";
 import { InsightRail } from "@/components/shared/InsightRail";
 import { apiFetch } from "@/lib/api";
 import { AlertTriangle, FileText, ClipboardList, ScrollText, Network, DollarSign, Activity, Users, Bot, Flag, Calendar, TrendingUp } from "lucide-react";
@@ -135,7 +134,6 @@ export default function WorkbenchPage() {
   const [activeTab, setActiveTab] = useState<TabId>("overview");
   const [detail, setDetail] = useState<CompanyDetail | null>(null);
   const [loading, setLoading] = useState(true);
-  const [workMode, setWorkMode] = useState<WorkMode>("overview");
 
   useEffect(() => {
     if (!companyId) return;
@@ -177,11 +175,6 @@ export default function WorkbenchPage() {
         pendingTasks={pendingTasksCount}
       />
 
-      {/* Work Mode 切换器 */}
-      <div className="flex items-center justify-between">
-        <WorkModeSwitcher mode={workMode} onChange={setWorkMode} />
-      </div>
-
       {/* 主内容 + Insight Rail */}
       <div className="flex gap-0">
         {/* Tab 导航 + 内容 */}