Brings the Tauri 2.x tray popover from #1022 onto main as windows/, mirroring
mac/. Product name, bundle identifier, and version line up with the macOS
menubar (org.agentseal.codeburn-menubar, 0.9.20); the crate is renamed off
"desktop" so it no longer collides with the Electron app in app/.
Linux (ksni) stays compiled and dev-usable but is documented as experimental:
gnome/ is the shipping Linux surface.
The five src/ CLI commits on that branch are dropped - they re-implement a
daily-bucketing fix main already carries.
