Bug: Sheet modals with showBackdrop=false in child routes block parent page interaction

Bug: Sheet modals with showBackdrop=false in child routes block parent page interaction: a task in LegoFlow-SWE (Harbor dataset). When a sheet modal with showBackdrop=false is rendered inside a child route (via a nested <ion-router-outlet ), the parent page content becomes completely…

The task

When a sheet modal with `showBackdrop=false` is rendered inside a child route (via a nested `<ion-router-outlet>`), the parent page content becomes completely non-interactive. Clicking buttons or other elements in the parent component has no effect, even though `showBackdrop=false` should permit background interaction.

Part of Lego-X/LegoFlow-SWE.