[Tracking] Windows Desktop GUI: console windows (cmd/conhost/git/gh/powershell) flash on subprocess spawns

This tracking issue consolidates roughly 25 reports of console windows (cmd, conhost, git, gh, powershell) flashing on the Windows desktop GUI when its windowless pythonw.exe backend spawns console-subsystem child processes without the no-window flag, and documents which spawn sites are still leaking based on source and git-history verification.