feat(desktop): DeerFlow visual redesign + stream hang fix + intelligence client

DeerFlow frontend visual overhaul:
- Card-style input box (white rounded card, textarea top, actions bottom)
- Dropdown mode selector (闪速/思考/Pro/Ultra with icons+descriptions)
- Colored quick-action chips (小惊喜/写作/研究/收集/学习)
- Minimal top bar (title + token count + export)
- Warm gray color system (#faf9f6 bg, #f5f4f1 sidebar, #e8e6e1 border)
- DeerFlow-style sidebar (新对话/对话/智能体 nav)
- Reasoning block, tool call chain, task progress visualization
- Streaming text, model selector, suggestion chips components
- Resizable artifact panel with drag handle
- Virtualized message list for 100+ messages

Bug fixes:
- Stream hang: GatewayClient onclose code 1000 now calls onComplete
- WebView2 textarea border: CSS !important override for UA styles
- Gateway stream event handling (response/phase/tool_call types)

Intelligence client:
- Unified client with fallback drivers (compactor/heartbeat/identity/memory/reflection)
- Gateway API types and type conversions

desktop/pnpm-lock.yaml

@@ -41,6 +41,9 @@ importers:
       react-markdown:
         specifier: ^10.1.0
         version: 10.1.0(@types/react@19.2.14)(react@19.2.4)
+      react-resizable-panels:
+        specifier: ^4.8.0
+        version: 4.8.0(react-dom@19.2.4(react@19.2.4))(react@19.2.4)
       react-window:
         specifier: ^2.2.7
         version: 2.2.7(react-dom@19.2.4(react@19.2.4))(react@19.2.4)
@@ -2819,6 +2822,12 @@ packages:
     resolution: {integrity: sha512-z6F7K9bV85EfseRCp2bzrpyQ0Gkw1uLoCel9XBVWPg/TjRj94SkJzUTGfOa4bs7iJvBWtQG0Wq7wnI0syw3EBQ==}
     engines: {node: '>=0.10.0'}
 
+  react-resizable-panels@4.8.0:
+    resolution: {integrity: sha512-2uEABkewb3ky/ZgIlAUxWa1W/LjsK494fdV1QsXxst7CDRHCzo7h22tWWu3NNaBjmiuriOCt3CvhipnaYcpoIw==}
+    peerDependencies:
+      react: ^18.0.0 || ^19.0.0
+      react-dom: ^18.0.0 || ^19.0.0
+
   react-window@2.2.7:
     resolution: {integrity: sha512-SH5nvfUQwGHYyriDUAOt7wfPsfG9Qxd6OdzQxl5oQ4dsSsUicqQvjV7dR+NqZ4coY0fUn3w1jnC5PwzIUWEg5w==}
     peerDependencies:
@@ -6213,6 +6222,11 @@ snapshots:
 
   react-refresh@0.17.0: {}
 
+  react-resizable-panels@4.8.0(react-dom@19.2.4(react@19.2.4))(react@19.2.4):
+    dependencies:
+      react: 19.2.4
+      react-dom: 19.2.4(react@19.2.4)
+
   react-window@2.2.7(react-dom@19.2.4(react@19.2.4))(react@19.2.4):
     dependencies:
       react: 19.2.4