feat(school-detail): icon-only Compare on phone heroes; unclutter map bottom edge

On ≤640px the floating Compare button becomes a 40px round glyph (+ / ✓,
aria-labelled) like the section-nav compare icon, instead of a full-width
text pill over the map. The OSM attribution moves to the map band's
top-left in preview so it no longer collides with the school name sliding
up under the fade; fullscreen keeps Leaflet's default bottom-right since
the zoom control occupies the top-left there.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

nextjs-app/components/SchoolHeroMap.module.css

@@ -16,6 +16,17 @@
     }
 }
 
+/* Preview: move the OSM attribution off the bottom edge, where the school
+   title slides up under the fade — top-left is the band's only quiet corner
+   (Compare floats top-right). Fullscreen keeps Leaflet's default bottom-right,
+   since the zoom control occupies the top-left there. */
+.wrapper:not([data-fullscreen]) :global(.leaflet-bottom.leaflet-right) {
+    top: 0;
+    left: 0;
+    right: auto;
+    bottom: auto;
+}
+
 /* Fullscreen: the Fullscreen API promotes this element to fill the viewport. */
 .wrapper[data-fullscreen] {
     height: 100vh;