6869d009c9
On Windows Desktop the hidden tier-2 link-title BrowserWindow has still painted a blank top-level frame over the chat during browser-tool turns (#64867). Encode the invisibility contract in the launch options — off-screen bounds, skipTaskbar, focusable: false — and belt-and-suspenders it with setOpacity(0) + hide() after creation, best-effort like the audio mute. Salvaged from #66523 (thanks @stantheman0128).