fix: 修复 Windows Codex 进程完成后不自动退出问题 (v1.7.21)

问题根因:
1. messageTimerCh 中阻塞等待 waitCh 导致无限挂起
2. Windows 上 proc.Kill() 只杀主进程不杀子进程

解决方案:
1. 移除 messageTimerCh case 中的阻塞等待
2. 新增 killProcessTree() 使用 taskkill /T /F /PID 终止进程树
3. 修改 terminateCommand/terminateProcess/forwardSignals 使用进程树终止

codeagent-wrapper/main_test.go

@@ -3067,7 +3067,7 @@ func TestVersionFlag(t *testing.T) {
 		}
 	})
 
-	want := "codeagent-wrapper version 5.4.0\n"
+	want := "codeagent-wrapper version 5.6.0\n"
 
 	if output != want {
 		t.Fatalf("output = %q, want %q", output, want)
@@ -3083,7 +3083,7 @@ func TestVersionShortFlag(t *testing.T) {
 		}
 	})
 
-	want := "codeagent-wrapper version 5.4.0\n"
+	want := "codeagent-wrapper version 5.6.0\n"
 
 	if output != want {
 		t.Fatalf("output = %q, want %q", output, want)
@@ -3099,7 +3099,7 @@ func TestVersionLegacyAlias(t *testing.T) {
 		}
 	})
 
-	want := "codex-wrapper version 5.4.0\n"
+	want := "codex-wrapper version 5.6.0\n"
 
 	if output != want {
 		t.Fatalf("output = %q, want %q", output, want)