cal_ocr_word_box returned the line's per-character probabilities, spaces
included, as the word scores, so word n got the probability of character n
of the line. Keep each word's character probabilities in
WordInfo.char_confs and score a grouped word with their mean, like the line
score; a single character keeps its own probability.
Co-authored-by: Paul Faucher <186776257+pfauch741@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
