Hello work 0.8.3 — alert no longer kills the app

Fix

Typing a custom grace value above 30 minutes was supposed to show a friendly «that defeats the purpose» alert. Instead the settings window went unresponsive and could only be killed from the menu bar.

Root cause: when the alert tried to attach as a sheet, the parent window briefly lost key status. Our auto-close-on-blur handler fired before the sheet was actually attached, killed the window mid-presentation, and the alert was orphaned.

The handler now waits a runloop tick and checks attachedSheet / modalWindow / isKeyWindow before closing. Sheets and dialogs across the app (alerts, app picker, future popups) are protected.