fix(windows): preserve image validation stderr

[nightt5879]

Summary / 摘要

• Route Windows image-metadata validation through the existing Invoke-DreamSkinNative compatibility wrapper instead of invoking Node with a direct 2>&1 redirection.
• Discard helper stderr while preserving stdout and the real exit code, so harmless Node warnings cannot terminate PowerShell 5.1 or corrupt the JSON metadata result.
• Preserve the existing friendly size-safety error for invalid images.
• Add a real PowerShell 5.1 regression that injects Node stderr on both successful and failing metadata checks.

Root cause / 根因

Windows PowerShell 5.1 promotes redirected native stderr to ErrorRecord objects. With $ErrorActionPreference = 'Stop', the direct image-helper invocation could terminate on its first stderr line before reading $LASTEXITCODE, bypassing the repository's native-command compatibility layer and its stable validation message.

Type / 类型

• Bug fix / 缺陷修复
• Feature / 新功能
• Docs / 文档
• Theme / CSS / visual / 主题或视觉
• Scripts / install / restore / 脚本或安装恢复
• Chore / 杂项

Platform / 平台

• macOS
• Windows
• Both / 双平台
• Docs / repo only / 仅文档或仓库元数据

Self-check / 自测

Check what you actually ran. Skip items that do not apply and say so under Notes.
请勾选实际跑过的项；不适用的在 Notes 说明。

Docs-only / 仅文档

• Links and wording reviewed / 已检查链接与表述

macOS (when code under macos/ changes)

• macos/tests/run-tests.sh passed / 已通过
• Doctor (optional): macos/scripts/doctor-macos.sh
• Live verify (if inject/CSS/start path): verify-dream-skin-macos.sh or Desktop Verify
• Restore / re-apply smoke (if install/restore/start changed) / 若改了安装恢复启动则做过恢复再应用

Windows (when code under windows/ changes)

• Relevant install / start / verify / restore scripts exercised / 已按改动跑过对应脚本
• Environment noted below (OS build, Codex source) / 下方注明环境

User-facing / 用户可见变更

• Updated macos/CHANGELOG.md (and macos/VERSION if release-worthy) / 已更新 changelog（发版时再 bump VERSION）
• N/A — no user-facing change / 无用户可见变更

Security / 安全

• Does not modify official Codex install / asar / signatures / 未修改官方安装与签名
• Does not silently write API Base URL or keys / 未静默写入 API Base URL 或 Key
• CDP remains loopback-oriented (127.0.0.1) where applicable / CDP 仍仅本机回环（如适用）

Notes / 补充

• Passed twice: powershell.exe -NoProfile -ExecutionPolicy Bypass -File .\windows\tests\run-tests.ps1.
• The regression uses a Node data: preload to emit stderr under $ErrorActionPreference = 'Stop'; a valid image still parses, while an invalid image returns the friendly Image metadata is invalid or exceeds... error rather than NativeCommandError.
• The warning lines in the suite output are expected fault-injection coverage for runtime and atomic-cleanup failure paths.
• Passed: PowerShell parser checks for the changed scripts and git diff --check.
• Updated windows/CHANGELOG.md; the template's changelog checkbox is macOS-specific.
• Environment: Windows 11 build 26200; Windows PowerShell 5.1.26100.8875; Node.js 22.22.2.
• No live Codex restart or renderer injection was needed because the change is isolated to pre-import image validation.

Fixes #112

[Fei-Away]

Closing — #112 (what this PR was meant to fix) was already resolved through a different change, so this PR has nothing left to land. Thanks for the contribution!

关闭：这个 PR 对应的 #112 已经通过其他改动解决了，这个 PR 不需要再合并了。感谢你的贡献！