Update downloads never used the configured proxy because electron-updater
runs all traffic on its own session partition, while the proxy was applied
to app/defaultSession only. Point proxy config at autoUpdater.netSession,
and make the system fallback an explicit `mode: 'system'` since an empty
setProxy config means fixed_servers with no rules (= direct), which also
silently downgraded the default session away from the OS proxy.
Disable differential download: blockmap-driven ranged requests against the
GitHub CDN are RTT-bound and run far below line speed on both macOS and
Windows; full downloads restore expected bandwidth.
Guard captureWindowState and the resize forwarder against destroyed
windows: quitAndInstall tears the window down while late move/resize/close
events still fire, crashing the main process with "Object has been
destroyed".
Widen the About page container from max-w-lg to max-w-2xl so release notes
markdown is no longer cramped.