The desktop app opens again

3.8.5 shipped a desktop app that opened to "This view stopped" on every platform. Sorry about that. This release fixes it, explains what happened, and adds the checks that stop it from happening again. Update, and the app opens the way it did before.

• The desktop window comes up alive on macOS, Windows, and Linux. A piece of command-line code slipped into the desktop window in 3.8.5, where it cannot run, and the window died the moment it opened. It is out. The build now refuses that class of mistake outright, so it cannot reach a release again.
• Every release is launched before it ships. The release check used to confirm that a window appeared. It now boots the packaged app on macOS and on a real Windows machine, waits for the interface inside the window, and refuses to ship if it does not come up.

• Older releases stay downloadable. The download page now lists the two releases before the current one, with checksums and notes, so a bad update always has a way back.

Everything from 3.8.5 still stands: your sign-ins and keys are back on Linux and macOS, YOLO mode switches on and off instantly, and the Chrome extension is found and repaired on its own.