feat(ui): vs-AI comms trim, overlay confirm button, recall-to-slot drag

- vs-AI: the comms hub drops the Chat tab (Dictionary only); a finished AI
  game has no comms at all, so its 💬 history-header entry is hidden too.
- Confirm-move ✅: redone as an absolute overlay pinned to the right edge (its
  right edge sits under the preview caption), so the rack keeps a fixed tile
  size — this reverts the tile-shrink that resized the letters at 6 tiles.
- Recall: dragging a placed tile back to the rack now drops it at the slot the
  pointer is over (drag-to-position, a gap opens), instead of snapping to its
  original slot; double-tap still recalls to the origin. New pure recallToSlot.

Tests: placement recallToSlot units; e2e recall-to-position; vs-AI comms e2e
updated. Docs: UI_DESIGN + FUNCTIONAL (+ru).

ui/src/lib/placement.ts

@@ -102,6 +102,51 @@ export function recallIndex(p: Placement, rackIndex: number): Placement {
   return { ...p, pending: p.pending.filter((t) => t.rackIndex !== rackIndex) };
 }
 
+/**
+ * recallToSlot recalls the pending tile at (row, col) and reinserts its rack letter at the
+ * given visible slot, reordering the rack the way a drag-to-reorder does (the drop position the
+ * player chose) instead of snapping the tile back to its original slot. It returns the new
+ * placement together with the index permutation applied to the rack, so the caller can permute
+ * its parallel stable ids in lockstep. toSlot counts the slots that stay visible after the
+ * recall (those still on the board are skipped); it is clamped to a valid position. The result
+ * is the unchanged placement and an identity permutation when no pending tile sits at (row, col).
+ */
+export function recallToSlot(
+  p: Placement,
+  row: number,
+  col: number,
+  toSlot: number,
+): { placement: Placement; order: number[] } {
+  const identity = p.rack.map((_, i) => i);
+  const tile = p.pending.find((t) => t.row === row && t.col === col);
+  if (!tile) return { placement: p, order: identity };
+  const ri = tile.rackIndex;
+  const rest = p.pending.filter((t) => t !== tile);
+  const usedByRest = new Set(rest.map((t) => t.rackIndex));
+  // Reinsert ri just before the toSlot-th slot that stays visible after the recall.
+  const others = identity.filter((i) => i !== ri);
+  let visible = 0;
+  let insertPos = others.length;
+  for (let pos = 0; pos < others.length; pos++) {
+    if (usedByRest.has(others[pos])) continue;
+    if (visible === toSlot) {
+      insertPos = pos;
+      break;
+    }
+    visible++;
+  }
+  const order = [...others];
+  order.splice(insertPos, 0, ri);
+  const newIndex = new Map(order.map((oldIdx, idx) => [oldIdx, idx]));
+  return {
+    placement: {
+      rack: order.map((i) => p.rack[i]),
+      pending: rest.map((t) => ({ ...t, rackIndex: newIndex.get(t.rackIndex)! })),
+    },
+    order,
+  };
+}
+
 export function reset(p: Placement): Placement {
   return { ...p, pending: [] };
 }