window.confirm bug in Electron

[tsiger]

window.confirm in the two navigation-guard hooks triggers Electron's Windows focus bug; the fix is swapping it for the in-app confirm modal

[tsiger]

The "You have unsaved changes" prompt used the browser's built-in window.confirm(). On Windows, Electron has a long-standing bug where dismissing a native dialog leaves the window thinking it lost focus — every input still looks normal but you can't click into it or type until you alt-tab away and back.

It's an upstream Electron bug, confirmed by their maintainers, open since 2019 and still broken in the latest versions (#31917, #40212, #41603). Windows only — Mac and the web app were never affected. No fix is coming, so we stopped using the native dialog.

Both navigation guards now use an in-app modal instead (same one as our delete confirmations). While we were in there, that modal got proper accessibility and focus handling — Escape to cancel, focus trapped inside it, and focus handed back to whatever you clicked when it closes.