feat: DeerFlow 2.0 core capabilities — Phase 1.0 + 1.1

Phase 1.0 — Butler Mode UI:
- Hide "自动化" and "技能市场" entries from sidebar navigation
- Remove AutomationPanel and SkillMarket view rendering from App.tsx
- Simplify MainViewType to only 'chat'
- Main interface is now: chat + conversation list + detail panel only

Phase 1.1 — Mode Differentiation:
- Add subagent_enabled field to ChatModeConfig (Rust), StreamChatRequest (Tauri),
  gateway-client, kernel-client, saas-relay-client, and streamStore
- TaskTool is now only registered when subagent_enabled=true (Ultra mode)
- System prompt includes sub-agent delegation instructions only in Ultra mode
- Frontend transmits subagent_enabled from ChatMode config through the full stack

This connects the 4-tier mode selector (Flash/Thinking/Pro/Ultra) to actual
backend behavioral differences — Ultra mode now truly enables sub-agent delegation.

desktop/src/lib/gateway-client.ts

@@ -476,6 +476,7 @@ export class GatewayClient {
       thinking_enabled?: boolean;
       reasoning_effort?: string;
       plan_mode?: boolean;
+      subagent_enabled?: boolean;
     }
   ): Promise<{ runId: string }> {
     const agentId = opts?.agentId || this.defaultAgentId;
@@ -489,6 +490,7 @@ export class GatewayClient {
         thinking_enabled: opts?.thinking_enabled,
         reasoning_effort: opts?.reasoning_effort,
         plan_mode: opts?.plan_mode,
+        subagent_enabled: opts?.subagent_enabled,
       };
       this.fetchDefaultAgentId().then(() => {
         const resolvedAgentId = this.defaultAgentId;
@@ -529,6 +531,7 @@ export class GatewayClient {
       thinking_enabled?: boolean;
       reasoning_effort?: string;
       plan_mode?: boolean;
+      subagent_enabled?: boolean;
     }
   ): void {
     // Close existing connection if any
@@ -570,6 +573,9 @@ export class GatewayClient {
         if (chatModeOpts?.plan_mode !== undefined) {
           chatRequest.plan_mode = chatModeOpts.plan_mode;
         }
+        if (chatModeOpts?.subagent_enabled !== undefined) {
+          chatRequest.subagent_enabled = chatModeOpts.subagent_enabled;
+        }
         this.zclawWs?.send(JSON.stringify(chatRequest));
       };