fix(windows): QA 浮窗显示时不再抢前台焦点

[appergb]

摘要

Closes #164

把 Windows 上 QA 浮窗的显示路径从普通 window.show() 改成 SW_SHOWNOACTIVATE + SWP_NOACTIVATE，避免多轮追问时 QA 浮窗抢成前台，后续抓选区读到自家 webview。

改动

• show_qa_window 新增 Windows 专用 show_qa_window_no_activate
• 直接从 WebviewWindow 读取 HWND，不靠窗口标题猜句柄
• 失败时保留 window.show() fallback，避免把窗口彻底显示不出来

验证

• cargo check --manifest-path src-tauri/Cargo.toml ✅
• Windows 语义依赖 CI / 实机验证

@codex review

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