Polish the tutor, log, and simple themes

[namest504]

Summary

• tutor: hands redrawn with distinct rounded fingers (box-drawing art with correct right-hand mirroring, ASCII fallback keeps the old art), and the keyboard now stays on the result screen with the stats where the sentence was
• log: background timestamps spread realistically into the past instead of one frozen second, and the round ends as proper daemon log lines (session complete + process exited)
• simple: the sentence sits vertically centered, and the copy matches the rest of the app (esc menu / ⏎ next)