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).

ui/e2e/landscape.spec.ts

@@ -26,10 +26,10 @@ test('landscape lays the game in two columns with the history docked open', asyn
   await expect(page.locator('.leftpane .tabbar')).toBeVisible();
 });
 
-test('landscape disables board zoom (a double-tap does not enlarge the board)', async ({ page }) => {
+test('landscape zooms the board on a double-tap and the zoomed board overflows the pane', async ({ page }) => {
   await openGame(page);
-  // Double-tap an empty cell: in portrait this zooms the board; in landscape it must not, because
-  // the whole board already fits by height.
+  // Double-tap an empty cell zooms in, same as portrait. The board is height-driven here, so the
+  // zoomed square grows past the wide pane and becomes pannable (scrollWidth exceeds the viewport).
   await page
     .locator('[data-cell]:not(.filled)')
     .nth(20)
@@ -37,8 +37,11 @@ test('landscape disables board zoom (a double-tap does not enlarge the board)',
       el.click();
       el.click();
     });
-  await page.waitForTimeout(300);
-  await expect(page.locator('.viewport.zoomed')).toHaveCount(0);
+  const viewport = page.locator('.viewport.zoomed');
+  await expect(viewport).toBeVisible();
+  await page.waitForTimeout(350); // let the width/height magnify settle
+  const overflows = await viewport.evaluate((el) => el.scrollWidth > el.clientWidth + 5);
+  expect(overflows).toBe(true);
 });
 
 test('landscape still places a tile and commits via the make button', async ({ page }) => {