Fix race condition causing "panic: send on closed channel"

[Copilot]

Problem

Race condition between worker goroutines adding tasks and main goroutine closing the task channel causes panic when processing deep search results.

Failure sequence:

Worker: processTask() → wg.Done() → AddTask() (tries to send)
Main:   wg.Wait() completes → closeCH() → closes taskCh
Worker: panic: send on closed channel

Changes

• Added closed flag to EnJob struct to track channel lifecycle
• Modified AddTask() and reTaskQueue(): Check closed flag under lock, increment wait group, release lock, then send to channel
• Modified closeCH(): Set closed flag before closing channels, prevent double-close

Safety

Wait group increment happens before lock release. Since closeCH() is only called after wg.Wait() completes, the channel is guaranteed open during send:

func (q *EnJob) AddTask(task DeepSearchTask) {
    q.mu.Lock()
    if q.closed {
        q.mu.Unlock()
        return
    }
    q.wg.Add(1)  // Prevents channel close
    q.mu.Unlock()
    q.taskCh <- task  // Safe: wg blocks closeCH()
}

Lock is released before channel send to prevent deadlock when channel is full.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>panic: send on closed channel</issue_title>
<issue_description>搜索比如温州大学时会有这个报错
panic: send on closed channel

goroutine 32 [running]:
github.com/wgpsec/ENScan/runner.(*EnJob).AddTask(0xc00021c1b0, {{{0xc000350a20, 0x24}, {0xc0005a2887, 0xe}, {0xc00018aa10, 0x67}, 0x2, {0xf84131, 0x6}, ...}, ...})
/home/runner/work/ENScan_GO/ENScan_GO/runner/bean.go:134 +0x45
github.com/wgpsec/ENScan/runner.(*EnJob).processTask(0xc00021c1b0, {{{0xc000031320, 0x24}, {0xc00056c481, 0xe}, {0xc0006104b0, 0x4f}, 0x1, {0xf84131, 0x6}, ...}, ...})
/home/runner/work/ENScan_GO/ENScan_GO/runner/enscan.go:171 +0x487
github.com/wgpsec/ENScan/runner.(*EnJob).StartWorkers.func1()
/home/runner/work/ENScan_GO/ENScan_GO/runner/bean.go:150 +0xa6
created by github.com/wgpsec/ENScan/runner.(*EnJob).StartWorkers in goroutine 16
/home/runner/work/ENScan_GO/ENScan_GO/runner/bean.go:143 +0x4f</issue_description>

Comments on the Issue (you are @copilot in this section)

@keac 请师傅详细列下查询的命令和使用程序的版本号

• Fixes panic: send on closed channel #211

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