feat(ui): landscape two-column game layout, board fitted by height

When the viewport is wider than tall (matchMedia orientation: landscape) the
game screen switches from the portrait stack to a two-column layout: the board
fills the right column as the largest square that fits the height (no zoom,
shrinking by width when cramped — lowest priority), while the left panel stacks
the rack (+ make), the status line, the score plaques, the always-open docked
history and the controls. Board zoom, the history slide-drawer gestures and the
growing nav bar are gated off in landscape; the portrait layout is unchanged and
both render from the same snippets so behaviour stays single-sourced.

The mock e2e now defaults to a portrait viewport (the mobile-first app the
gesture/zoom/history specs are written for); landscape.spec.ts covers the wide
layout in its own viewport.

ui/src/game/Rack.svelte

@@ -8,6 +8,7 @@
     slots,
     variant,
     selected,
+    landscape = false,
     shuffling = false,
     draggingId = null,
     dropIndex = null,
@@ -18,6 +19,9 @@
     slots: (RackSlot & { id: number })[];
     variant: Variant;
     selected: number | null;
+    /** Landscape layout: size the tiles to share the (narrow) left-panel width instead of the
+     *  viewport-width measure, so seven tiles never overflow the panel. */
+    landscape?: boolean;
     shuffling?: boolean;
     // While a rack tile is being dragged to reorder it, draggingId is its id (hidden here —
     // the drag ghost stands in) and dropIndex is the slot where a gap opens.
@@ -52,7 +56,7 @@
   }
 </script>
 
-<div class="rack" class:reordering={draggingId != null} data-rack>
+<div class="rack" class:reordering={draggingId != null} class:landscape data-rack>
   {#each shown as slot, i (slot.id)}
     <button
       class="tile"
@@ -100,6 +104,15 @@
     outline: 3px solid var(--accent);
     outline-offset: -3px;
   }
+  /* Landscape: the rack sits in a fixed-width left panel, so the tiles share the panel width
+     (capped at the portrait size) and shrink below it when the panel is narrow, instead of the
+     viewport-width measure that would overflow seven tiles in a column. */
+  .rack.landscape .tile {
+    flex: 1 1 0;
+    width: auto;
+    min-width: 0;
+    max-width: 46px;
+  }
   /* While reordering, tiles at/after the drop slot slide right to open a gap there (one
      tile width plus the rack gap), so the drop position is visible. */
   .rack.reordering .tile {