feat: 工具执行超时可配置 + 修复硬编码盖过工具自定义超时的 bug

1. 新增 agent.toolExecutionTimeoutMs 配置（默认 120s，范围 10~600s），AgentSettings 加输入框

2. 修复 engine.ts 硬编码 120s 会盖过 delegate-task(5min)/web-search(5min) 等工具自定义 timeoutMs 的 bug：改为取 max(配置值, tool.timeoutMs)

3. main.ts 启动时从 ConfigService 加载；handlers.ts 监听 config:set 即时更新

electron/main.ts

@@ -228,6 +228,7 @@ async function initialize(): Promise<void> {
   const agentTimeout = configService.get<number>('agent.totalTimeoutMs');
   const agentThinkingEnabled = configService.get<boolean>('agent.enableThinking');
   const agentThinkingEffort = configService.get<string>('agent.thinkingEffort') as 'low' | 'medium' | 'high' | 'max' | null;
+  const toolExecTimeout = configService.get<number>('agent.toolExecutionTimeoutMs');
   const agentLoop = new AgentLoopEngine(
     {
       maxIterations: agentMaxIter ?? 20,
@@ -235,6 +236,7 @@ async function initialize(): Promise<void> {
       contextLength: ollamaNumCtx ?? undefined,
       thinkingEnabled: agentThinkingEnabled ?? true,
       thinkingEffort: agentThinkingEffort ?? 'high',
+      toolExecutionTimeoutMs: toolExecTimeout ?? 120_000,
     },
     adapter, toolRegistry, preToolHooks, postToolHooks,
   );