feat(ui): move in-game status to the board — highlight, score badge, full-width rack

Remove the under-board status strip and relocate its signals:
- bag count -> a badge on the exchange/pass control + the foot of the move table
- whose-turn / win-lose -> a thin strip above the score plaques
- the tentative-move caption -> the board itself: staged tiles tint green (legal) or
  pink (illegal), the board tiles a formed word runs through go a shade darker, and an
  orange score badge sits on the main word (digit sized like a tile value, clamped on-board)

The word geometry (covered cells + badge anchor) is a new pure client-side helper
(ui/src/lib/formed.ts), independent of the move evaluator, so it works on the local or
network preview path alike; the badge's number still comes from the preview score.

Rack: a seven-column grid filling the tray width in both layouts — square, full-width
tiles — with the confirm control in the fixed 7th slot.

Settings: a touch-only "Zoom the board" toggle (default on, device-local) gates the
tile-placement auto-zoom; taking a hint while zoomed in now zooms out so the highlighted
hint word is never left off-screen.

Docs (FUNCTIONAL +_ru, UI_DESIGN, ARCHITECTURE) and e2e/unit tests updated.

ui/src/game/Board.svelte

@@ -23,6 +23,9 @@
     focus,
     recenter,
     dropTarget,
+    previewLegal,
+    formed,
+    scoreBadge,
     oncell,
     ontogglezoom,
     onrecall,
@@ -48,6 +51,15 @@
     recenter: number;
     /** The cell a dragged tile is currently aimed at, highlighted as a drop target. */
     dropTarget: { row: number; col: number } | null;
+    /** While composing: true when the staged tiles form a legal play, false when not, null when
+     *  there is no preview (off-turn, nothing staged, or a recall drag) — tints the pending tiles
+     *  green vs a calm pink. */
+    previewLegal: boolean | null;
+    /** "row,col" keys of every committed board cell a formed word runs through, greened a shade
+     *  darker than the player's own staged tiles. */
+    formed: Set<string>;
+    /** The orange move-score badge for the legal play being composed, or null. */
+    scoreBadge: { row: number; col: number; corner: 'tr' | 'bl'; score: number } | null;
     oncell: (row: number, col: number) => void;
     ontogglezoom: (row: number, col: number) => void;
     /** Recall the pending tile at (row, col) — fired on a double-tap of a pending cell. */
@@ -60,6 +72,20 @@
   const z = $derived(zoomed ? Z : 1);
   const premClass: Record<Premium, string> = { '': '', TW: 'tw', DW: 'dw', TL: 'tl', DL: 'dl' };
 
+  // The score badge sits on a corner of its anchor cell, clamped so the whole pill stays on the
+  // board. Its position is a percentage of the (15-cell) board; CSS centres the pill on the point.
+  const BADGE_MARGIN = 2.4;
+  const badgePos = $derived.by(() => {
+    const b = scoreBadge;
+    if (!b) return null;
+    const cell = 100 / 15;
+    let x = b.corner === 'tr' ? (b.col + 1) * cell : b.col * cell;
+    let y = b.corner === 'tr' ? b.row * cell : (b.row + 1) * cell;
+    x = Math.max(BADGE_MARGIN, Math.min(100 - BADGE_MARGIN, x));
+    y = Math.max(BADGE_MARGIN, Math.min(100 - BADGE_MARGIN, y));
+    return { x, y };
+  });
+
   let viewport = $state<HTMLElement>();
 
   // Genuine layout zoom (the board grows; cqw labels stay constant), so native scroll
@@ -315,6 +341,9 @@
             class="cell {premClass[premium[r][c]]}"
             class:filled={!!cell}
             class:pending={!!p && !cell}
+            class:legal={!!p && !cell && previewLegal === true}
+            class:illegal={!!p && !cell && previewLegal === false}
+            class:formed={!!cell && formed.has(key(r, c))}
             class:hl={!!cell && highlight.has(key(r, c)) && !flash}
             class:flash={!!cell && flash && highlight.has(key(r, c))}
             class:dark={premium[r][c] === '' && !cell && !p && (r + c) % 2 === 1}
@@ -342,6 +371,9 @@
           </button>
         {/each}
       {/each}
+      {#if scoreBadge && badgePos}
+        <span class="scorebadge" style="left:{badgePos.x}%; top:{badgePos.y}%">{scoreBadge.score}</span>
+      {/if}
     </div>
   </div>
 </div>
@@ -397,6 +429,8 @@
     gap: 0;
     background: var(--board-bg);
     padding: 0;
+    /* Anchor for the absolutely-positioned score badge (its percentages resolve against the board). */
+    position: relative;
   }
   .cell {
     position: relative;
@@ -445,6 +479,19 @@
        board) instead of the touch starting a board pan. */
     touch-action: none;
   }
+  /* While composing, the staged play recolours its tiles: a calm reddish-pink when they form no
+     word, a light green for the player's own tiles once they do; committed board tiles a formed
+     word runs through go a shade darker (see lib/formed + Game.svelte). .formed sits after .filled
+     so it wins on committed cells (equal specificity). */
+  .cell.pending.illegal {
+    background: var(--tile-pending-illegal);
+  }
+  .cell.pending.legal {
+    background: var(--tile-pending-legal);
+  }
+  .cell.formed {
+    background: var(--tile-formed);
+  }
   .cell.droptarget {
     /* The cell a carried tile is aimed at: an accent ring plus a light accent wash, so the
        target reads clearly while dragging without obscuring the bonus label underneath. */
@@ -545,4 +592,25 @@
     font-weight: 700;
     white-space: nowrap;
   }
+  /* The move-score badge for the legal play being composed: an orange pill centred on a corner of
+     the main word's tile (see lib/formed.badgePlacement + Game.svelte), its digit sized like a
+     tile's point value so it scales with the zoom. Decorative — no pointer events — and drawn above
+     the tiles. */
+  .scorebadge {
+    position: absolute;
+    transform: translate(-50%, -50%);
+    z-index: 5;
+    pointer-events: none;
+    border-radius: 999px;
+    background: var(--score-badge);
+    color: #fff;
+    font-weight: 700;
+    line-height: 1;
+    white-space: nowrap;
+    padding: 2px 5px; /* px fallback for Chrome < 105 (no cqw) */
+    padding: 0.4cqw 0.9cqw;
+    font-size: calc(2.4vmin * var(--z, 1)); /* cqw fallback for Chrome < 105 — see .letter */
+    font-size: 2.4cqw;
+    box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.25);
+  }
 </style>