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/game/Rack.svelte

@@ -83,12 +83,7 @@
   }
   .tile {
     position: relative;
-    /* Sit at the natural tile width, but shrink to fit when the row is crowded so a full
-       rack never overflows its wrapper onto the MakeMove control to its right (the confirm
-       button stays pinned at the right screen edge). flex-grow stays 0 so a sparse rack does
-       not stretch its tiles. */
-    flex: 0 1 auto;
-    min-width: 0;
+    flex: 0 0 auto;
     width: min(12.5vw, 46px);
     aspect-ratio: 1;
     background: var(--tile-bg);