A pane scrolls content taller than itself instead of clipping it away

The .pane clip (14096e19c) keeps a pane from painting outside its box,
but a profile with no scroller of its own then lost everything below the
pane's bottom: regions-mfe's regions list (rega RD3: last row at y1426 in
an 843 px pane; at 390 only Africa visible). Before the clip that content
spilled over the next pane instead. The pane mount now scrolls it at pane
height (overflow-y:auto), since a scroll container's scrollable area
includes its descendants' visible overflow; wheel and Tab reach it, and a
wheel at its end chains on to the column. Panes whose content fits (a
wall with its own scroller, a map) never scroll here.

library/layouts/pane-wrapper/pane-wrapper.js

@@ -80,6 +80,15 @@ export const PANE_GRID_STYLES = `
      over the map, and Tab into row 1 scrolled the COLUMN instead of the wall). Inherited, so it crosses
      into each element's shadow root, where no selector here can reach. */
   --profile-min-h:0;
+  /* ★ AND CONTENT TALLER THAN ITS PANE SCROLLS WITHIN IT. The clip on .pane (above) keeps a pane from
+     painting outside its box — but a profile with NO scroller of its own (regions-mfe's regions list:
+     its last row at y1426 in an 843 pane) then had everything below the pane's bottom UNREACHABLE,
+     where before it spilled over the next pane (rega RD3). The mount is pane-sized and a scroll
+     container's scrollable area includes its descendants' visible overflow, so such content now
+     scrolls here, at pane height; wheel and Tab reach it, and only at its end does a wheel chain on to
+     the column. A profile that already fits (a wall with its own scroller, a map) never scrolls here. */
+  overflow-y:auto;
+  overflow-x:hidden;
 }
 /* Placeholder copy for a pane whose profile is not built yet — same card styling
    as the wrapper's own placeholder so an unbuilt pane never looks broken. */