feat: add workbench shared utils, hooks, and display components

Phase 1-5: Created utils/workbench.js (STAGE_STATS_CONFIG eliminates
40+ repeated StatCards), useTaskStream hook (WebSocket event handling),
useTaskRunner hook (task start logic), StageStatsPanel, TaskControlPanel,
TaskProgressBar, TaskInfoPanel, TaskFileList, and TaskLogStream.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/hooks/useTaskRunner.js

@@ -0,0 +1,31 @@
+// frontend/src/hooks/useTaskRunner.js
+import { useState, useCallback } from 'react';
+import { runTask } from '../api/tasks';
+
+export default function useTaskRunner({ hydrateTask }) {
+  const [isStarting, setIsStarting] = useState(false);
+  const [errorMessage, setErrorMessage] = useState('');
+
+  const handleStart = useCallback(async (canStart) => {
+    if (!canStart) {
+      window.alert('请先在设置中配置目录！');
+      return;
+    }
+    setIsStarting(true);
+    setErrorMessage('');
+    try {
+      const response = await runTask();
+      await hydrateTask(response.task_id, true);
+    } catch (error) {
+      if (error.status === 409 && error.taskId) {
+        await hydrateTask(error.taskId, true);
+      } else {
+        setErrorMessage(error.message || '启动失败');
+      }
+    } finally {
+      setIsStarting(false);
+    }
+  }, [hydrateTask]);
+
+  return { isStarting, errorMessage, setErrorMessage, handleStart };
+}