feat(ui): landscape iteration — reorder left panel, enable board zoom

Left panel order is now score / history / status / rack / controls (the history
fills the middle and scrolls). Board zoom is re-enabled in landscape with the
same gestures as portrait, but height-driven: the viewport is the full right
pane, the board fits by height as a centred square when zoomed out, and on
zoom-in it magnifies past the pane and pans within it (focus-centred scroll that
rides the magnify transition), occupying the full width up to the left panel.
Board.svelte gains a landscape prop; portrait stays width-driven and unchanged.
landscape.spec.ts now asserts zoom works (the zoomed board overflows the pane).

docs/UI_DESIGN.md

@@ -134,14 +134,18 @@ Login uses `Screen`.
   keyboard-aware (they size to the area above the keyboard).
 - **Landscape (wide) layout** (`Game.svelte`): when the viewport is wider than tall
   (`matchMedia('(orientation: landscape)')`) the game switches from the portrait stack to a
-  **two-column** layout. The board fills the **right** column, fitted to the available height as
-  the largest square that still fits (`min(100cqw, 100cqh)` inside a `container-type: size` pane),
-  shrinking by width when the column is narrow — the board has the **lowest priority**, so the
-  left panel is never squeezed. The **left panel** stacks the rack (+ the ✅ make control), the
-  status line (bag · turn · score preview), the score plaques, the **always-open** history (docked
-  and scrolling with its header sticky — no slide-down drawer, no score-bar toggle) and, pinned at
-  the bottom, the controls tab bar. Board **zoom is disabled** (the whole board is already visible)
-  along with the history open/close swipes, and the nav bar does not grow (`growNav` off). The
+  **two-column** layout. The board fills the **right** column; it fits by **height** as a square
+  (`min(100cqw, 100cqh)`, height-driven in `Board.svelte`'s `.scaler.land`) inside a
+  `container-type: size` pane, shrinking by width when the column is narrow — the board has the
+  **lowest priority**, so the left panel is never squeezed. The **left panel** stacks, top to
+  bottom: the score plaques, the **always-open** history (docked and scrolling with its header
+  sticky — no slide-down drawer, no score-bar toggle), the status line (bag · turn · score
+  preview), the rack (+ the ✅ make control) and, pinned at the bottom, the controls tab bar. Board
+  **zoom works as in portrait** (double-tap / pinch / placement auto-zoom), but the viewport is the
+  full pane: zoom-out shows the height-fitted square centred, and zoom-in magnifies the board past
+  the pane and pans within it, occupying the full width up to the left panel (the focus-centred
+  scroll is set directly, without the portrait width-progress tween). Only the history open/close
+  swipes are dropped (it is always open) and the nav bar does not grow (`growNav` off). The
   portrait layout is byte-for-byte unchanged; both layouts render from the same snippets, so the
   behaviour and markup stay single-sourced. The rack tiles size to the (fixed-width) panel rather
   than the viewport width so seven tiles never overflow the column.