fix(layout): keep confirmation dialogs above map-control panels (#451) (#461)

* fix(layout): keep confirmation dialogs above map-control panels (#451)

Map-control panels (e.g. maplibre-gl-basemap-control) append their panel
to the map container with `position: absolute; z-index: 1000`. The map
area `<main>` was only `position: relative`, so that z-index escaped to
the root stacking context and rendered above body-portaled modal dialogs
(z-50) such as the layer-removal confirmation, leaving part of the dialog
unreadable behind the panel.

Make `<main>` an isolating stacking context (`isolation: isolate`) so all
map-control panels appended to the map container stay contained below the
modal layer. This fixes the reported basemap case and the whole class of
map-panel-over-dialog conflicts without touching the shadcn z-index scale
(so Radix popovers/selects nested inside dialogs keep working).

* Address Claude review feedback

- Condense the `<main>` isolate comment to a single line and correct the
  cited map-panel z-index from 1000 to 10000 (the four control-panel
  style sheets all use z-index: 10000).

Author: giswqs

apps/geolibre-desktop/src/components/layout/DesktopShell.tsx

@@ -1190,7 +1190,8 @@ export function DesktopShell({
           </SectionErrorBoundary>
         ) : null}
         <main
-          className={`relative min-w-0 flex-1 overflow-hidden ${
+          // `isolate` creates a stacking context so map-panel z-indexes (up to 10000) stay below body-portaled dialogs. See #451.
+          className={`relative isolate min-w-0 flex-1 overflow-hidden ${
             layoutOptions.compact ? "min-h-0" : "min-h-72 md:min-h-0"
           }`}
         >