scripts/desktop-update.ps1 moves to scripts/desktop-update/windows.ps1 (a
compat forwarder stays at the old path for one asar/checkout skew cycle)
and gains the shim: scripts/desktop-update/ui.html rendered in a
chromeless Edge app window, fed done|error over a loopback /progress
endpoint. The page is #75895's hand-off screen ported verbatim (Fourier
Flow loader, one title, one line, OS light/dark, charcoal dark seeds);
failure is the terse card pointing at hermes debug share. The WinForms
card stays as the no-Edge fallback, same shape.
Salvaged from the web-shell spike: TcpListener runspace server, Edge
--app spawn with throwaway profile, degradation ladder, -SelfTestUi.
Co-authored-by: Teknium <127238744+teknium1@users.noreply.github.com>