Merge pull request #416 from znygugeyx-ctrl/feat/subagent-fork-render

feat: 参考 claude code 官方实现，改进 sub agent 以及 fork agent 的渲染方式

src/hooks/useBackgroundAgentTasks.ts

@@ -0,0 +1,19 @@
+import { useMemo } from 'react'
+import { useAppState } from '../state/AppState.js'
+import {
+  isLocalAgentTask,
+  type LocalAgentTaskState,
+} from '../tasks/LocalAgentTask/LocalAgentTask.js'
+
+export function useBackgroundAgentTasks(): LocalAgentTaskState[] {
+  const tasks = useAppState(s => s.tasks)
+  return useMemo(() => {
+    const now = Date.now()
+    return Object.values(tasks)
+      .filter(isLocalAgentTask)
+      .filter(t => t.agentType !== 'main-session')
+      .filter(t => t.isBackgrounded !== false)
+      .filter(t => t.evictAfter === undefined || t.evictAfter > now)
+      .sort((a, b) => a.startTime - b.startTime)
+  }, [tasks])
+}