Entropy is now calculated from the pools each word was actually drawn
from: alliteration shrinks pools to words starting with the chosen
letter (plus log2(26) for the letter), function words contribute their
real list sizes, and the special-character pool is derived from
SPECIAL_CHARS minus the separator instead of a hardcoded 25. Also fixes
a "-Infinity bits" display when the capitalize slider exceeded the
word count.

Adds 36 tests for the previously untested strength functions (104
total) and raises coverage thresholds from 19/71/42/44 to 95% branches,
100% functions, 97% lines and statements.

Public-release cleanup: add MIT LICENSE, set package author, apply
Prettier across the repo, correct README security claims and test
counts, document the entropy estimate as an upper bound, check in
CLAUDE.md, and add a root TODO.md with the remaining review items.