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/src/lib/kernel-chat.ts

@@ -56,6 +56,9 @@ export function installChatMethods(ClientClass: { prototype: KernelClient }): vo
     opts?: {
       sessionKey?: string;
       agentId?: string;
+      thinking_enabled?: boolean;
+      reasoning_effort?: string;
+      plan_mode?: boolean;
     }
   ): Promise<{ runId: string }> {
     const runId = crypto.randomUUID();
@@ -68,6 +71,20 @@ export function installChatMethods(ClientClass: { prototype: KernelClient }): vo
     }
 
     let unlisten: UnlistenFn | null = null;
+    let completed = false;
+    // Stream timeout — prevent hanging forever if backend never sends complete/error
+    const STREAM_TIMEOUT_MS = 5 * 60 * 1000; // 5 minutes
+    const timeoutId = setTimeout(() => {
+      if (!completed) {
+        completed = true;
+        log.warn('Stream timeout — no complete/error event received');
+        callbacks.onError('响应超时，请重试');
+        if (unlisten) {
+          unlisten();
+          unlisten = null;
+        }
+      }
+    }, STREAM_TIMEOUT_MS);
 
     try {
       // Set up event listener for stream chunks
@@ -129,6 +146,8 @@ export function installChatMethods(ClientClass: { prototype: KernelClient }): vo
 
           case 'complete':
             log.debug('Stream complete:', streamEvent.inputTokens, streamEvent.outputTokens);
+            completed = true;
+            clearTimeout(timeoutId);
             callbacks.onComplete(streamEvent.inputTokens, streamEvent.outputTokens);
             // Clean up listener
             if (unlisten) {
@@ -139,6 +158,8 @@ export function installChatMethods(ClientClass: { prototype: KernelClient }): vo
 
           case 'error':
             log.error('Stream error:', streamEvent.message);
+            completed = true;
+            clearTimeout(timeoutId);
             callbacks.onError(streamEvent.message);
             // Clean up listener
             if (unlisten) {
@@ -155,6 +176,9 @@ export function installChatMethods(ClientClass: { prototype: KernelClient }): vo
           agentId,
           sessionId,
           message,
+          thinkingEnabled: opts?.thinking_enabled,
+          reasoningEffort: opts?.reasoning_effort,
+          planMode: opts?.plan_mode,
         },
       });
     } catch (err: unknown) {