Test strong high-density boards

[kevinatlee]

Summary

• add a separate 32-candidate strong board selector ranked by playable words, coverage, then generation order
• use the strong selector for round starts while preserving the median selector and targets
• let display result quips use available width on landscape/TV and wrap safely without portrait overflow
• add deterministic strong-selection audit tooling and results

Audit

500 selections per size, repeated byte-identically. Selected playable-word medians were 164, 307, and 479 for 4x4, 5x5, and 6x6, each above the retained original corpus P95.

Validation

• focused selector tests: 20 passed
• focused server tests: 42 passed
• focused results/style tests after portrait fix: 39 passed
• full repository tests: 817 passed
• complete local validation and production smoke passed
• exact-head CI and test-image publication passed at a42be61838cf59bcac6b7af258c091b5906fc583
• physical gameplay, TV, and portrait testing approved

Ready for squash merge to main.