fix(ci): 修复 PowerShell 执行策略检查逻辑

- 从检查 CurrentUser 范围改为检查有效执行策略
- 适配 NETWORK SERVICE 账户运行的 runner
- 已在 runner 机器上设置 LocalMachine 执行策略为 RemoteSigned

修复了 Windows 自托管 runner 的执行策略检测问题

.github/workflows/build-win-h5-only.yml

@@ -20,7 +20,7 @@ jobs:
       - name: 检查 PowerShell 执行策略
         shell: cmd
         run: |
-          powershell -Command "$policy = Get-ExecutionPolicy -Scope CurrentUser; Write-Host '当前执行策略：' $policy; if ($policy -eq 'Restricted' -or $policy -eq 'Undefined') { Write-Error '执行策略未正确配置！请在 runner 机器上执行：Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser -Force'; exit 1 } else { Write-Host '✓ 执行策略检查通过' }"
+          powershell -Command "$policy = Get-ExecutionPolicy; Write-Host '当前有效执行策略：' $policy; if ($policy -eq 'Restricted' -or $policy -eq 'Undefined') { Write-Error '执行策略未正确配置！请在 runner 机器上执行：Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope LocalMachine -Force'; exit 1 } else { Write-Host '✓ 执行策略检查通过' }"
 
       - name: Test SSH key
         shell: powershell