- Introduce BookworkSteering with context-aware letter placement: class
steering, vowel-band control, and a real-word completion boost so boards
stay playable and avoid dead/vowel-clumped states across refills.
- Make gold/diamond spawn chances configurable per level via a linear ramp
(specialTiles in bookwork.json), wiring the values through clearAndRefill
and refillSteered instead of hard-coded constants.
- Add verifyBookwormBoard harness comparing baseline vs steered boards on
word availability, dead-board rate, and simulated session survival, and
extend verifyBookwork with special-tile schedule checks.
