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/app.css

@@ -29,6 +29,14 @@
   --tile-edge: #d8c190;
   --tile-text: #2a2113;
   --tile-pending: #f2cf73;
+  /* In-composition highlight of the staged play (see game/Board.svelte): a calm reddish-pink
+     when the tiles form no word, a light green for the player's own tiles once they do, a
+     deeper green for the board tiles a formed word runs through, and the orange move-score
+     badge. Tuned per theme; refined on the contour. */
+  --tile-pending-illegal: #f2c7bf;
+  --tile-pending-legal: #c9e7bd;
+  --tile-formed: #a5cf93;
+  --score-badge: #e5811d;
   /* Last-word highlight letter — a lighter burgundy than the dark theme on purpose: against
      the lighter tile the perceived contrast needs it, so the two are tuned per theme. */
   --tile-recent: #9c5849;
@@ -84,6 +92,10 @@
     --tile-edge: #b6a473;
     --tile-text: #20190d;
     --tile-pending: #d8b75e;
+    --tile-pending-illegal: #d8a99f;
+    --tile-pending-legal: #a9cf94;
+    --tile-formed: #83b571;
+    --score-badge: #e88f31;
     --tile-recent: #8c4a3c;
     --prem-tw: #9c3f34; /* 3x word: a touch darker red */
     --prem-dw: #a8636b; /* 2x word: softer, pinker */
@@ -115,6 +127,10 @@
   --tile-edge: #b6a473;
   --tile-text: #20190d;
   --tile-pending: #f0d98f;
+  --tile-pending-illegal: #d8a99f;
+  --tile-pending-legal: #a9cf94;
+  --tile-formed: #83b571;
+  --score-badge: #e88f31;
   /* Last-word highlight letter — a warm burgundy whose red hue stays distinct from both the
      near-black glyph and the warm tile. The light theme uses a lighter burgundy (tuned per
      theme; perceived contrast depends on the surrounding board). */