Fix Anagrams: draggable center tiles, keyboard input, countdown animation, claim...

Fix Anagrams: draggable center tiles, keyboard input, countdown animation, claim bugs

1. Center tiles can be dragged to rearrange (client-side only,
   mouse and touch) to help visualize possible words.
2. Keyboard input during claiming: type letters to grab from
   center, Backspace to return last, Enter to submit, Escape
   to cancel.
3. Countdown shows 3, 2, 1 on the tile with opacity fade
   animation each second.
4. Fix cancelled claims not returning tiles to center (let
   server SSE events handle state cleanup).
5. Fix UI staying in claim mode after successful word submission
   (server-side fix: broadcast claim-end after acceptance).
Also remove game_steal references (deferred for later).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>