feat: deliverables 3-6 — cold start, simple mode UI, bridge tests, docs

Deliverable 3 — Cold Start Flow:
- New: use-cold-start.ts — cold start detection + greeting management
- Default Chinese greeting for hospital admin users
- Phase tracking: idle → greeting_sent → waiting_response → completed

Deliverable 4 — Simple Mode UI:
- New: uiModeStore.ts — 'simple'|'professional' mode with localStorage
- New: SimpleTopBar.tsx — minimal top bar with mode toggle
- Modified: App.tsx — dual layout rendering based on UI mode
- Modified: ChatArea.tsx — compact prop hides advanced controls
- Default: 'simple' mode for zero-barrier first experience

Deliverable 5 — Tauri Bridge Integration Tests:
- New: tauri-bridge.integration.test.ts — 14 test cases
- Covers: cold start, chat flow, persistence, memory, butler, UI mode, e2e
- 14/14 passing

Deliverable 6 — Release Documentation:
- New: installation-guide.md — user-facing install guide (Chinese, no jargon)
- New: hospital-deployment.md — IT admin deployment guide (Docker, GPO, SCCM)

desktop/src/App.tsx

@@ -27,6 +27,8 @@ import { useToast } from './components/ui/Toast';
 import type { Clone } from './store/agentStore';
 import { createLogger } from './lib/logger';
 import { startOfflineMonitor } from './store/offlineStore';
+import { useUIModeStore } from './store/uiModeStore';
+import { SimpleTopBar } from './components/SimpleTopBar';
 
 const log = createLogger('App');
 
@@ -443,6 +445,33 @@ function App() {
     );
   }
 
+  const uiMode = useUIModeStore((s) => s.mode);
+
+  // Simple mode: single-column layout with top bar only
+  if (uiMode === 'simple') {
+    return (
+      <div className="h-screen flex flex-col overflow-hidden text-gray-800 text-sm bg-white dark:bg-gray-950">
+        <SimpleTopBar onToggleMode={() => useUIModeStore.getState().setMode('professional')} />
+        <div className="flex-1 min-h-0">
+          <ChatArea compact />
+        </div>
+
+        {/* Hand Approval Modal (global) */}
+        <HandApprovalModal
+          handRun={pendingApprovalRun}
+          isOpen={showApprovalModal}
+          onApprove={handleApproveHand}
+          onReject={handleRejectHand}
+          onClose={handleCloseApprovalModal}
+        />
+
+        {/* Proposal Notifications Handler */}
+        <ProposalNotificationHandler />
+      </div>
+    );
+  }
+
+  // Professional mode: three-column layout (default)
   return (
     <div className="h-screen flex overflow-hidden text-gray-800 text-sm bg-white dark:bg-gray-950">
       {/* 左侧边栏 */}