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/ipc/handlers.ts

@@ -505,6 +505,10 @@ export function registerAllIPCHandlers(
       // 工具确认超时变更，即时应用到 ConfirmationHook
       confirmationHook.setConfirmationTimeout(value as number);
       log.info(`[CONFIG] Confirmation timeout updated to ${value}ms`);
+    } else if (key === 'agent.toolExecutionTimeoutMs') {
+      // 工具执行兜底超时变更，即时应用到 Engine
+      agentLoop.updateConfig({ toolExecutionTimeoutMs: value as number });
+      log.info(`[CONFIG] Tool execution timeout updated to ${value}ms`);
     }
 
     // 日志级别变更时即时应用
@@ -670,7 +674,7 @@ export function registerAllIPCHandlers(
 
   // 获取当前工作空间详情：路径 + 4 个核心文件状态 + 自动目录状态
   ipcMain.handle('workspace:getInfo', async () => {
-    const { existsSync, statSync } = await import('fs');
+    const { existsSync, statSync, readFileSync, readdirSync } = await import('fs');
     const workspacePath = workspaceService.getPath();
     const files = workspaceService.reload(); // 同步外部可能的手动修改
 
@@ -690,7 +694,6 @@ export function registerAllIPCHandlers(
           size = stat.size;
           mtime = stat.mtimeMs;
           // 截取前 500 字符作为预览
-          const { readFileSync } = await import('fs');
           const content = readFileSync(filePath, 'utf-8');
           preview = content.length > 500 ? content.slice(0, 500) + '\n...(已截断)' : content;
         }
@@ -718,7 +721,6 @@ export function registerAllIPCHandlers(
           exists = true;
           const stat = statSync(dirPath);
           if (stat.isDirectory()) {
-            const { readdirSync } = await import('fs');
             fileCount = readdirSync(dirPath).length;
           }
         }