anagrams: Fix claim interface to work for stealing a word

anagrams: Fix claim interface to work for stealing a word

Typing letters in the claim area now draws from stolen words first,
(if possible), and from the center area otherwise. Each letter used
from a stolen word is marked in accent-color-muted to show it has
been used. The backspace key or a little "X" badge can be used to
return letters from the rack back to where they came from.