Add desktop-backed confirm dialog API for worktree deletion

- add `dialogs.confirm` to native IPC/contracts and desktop preload/main bridge
- switch sidebar worktree deletion prompt from `window.confirm` to native API
- add `showDesktopConfirmDialog` helper with unit tests for dialog behavior
bc312825cfJulius Marminge committed on 2/13/2026, 6:42:01 AMparent6d9a467
8 files changedLine totals unavailable