Grids Game Implementation Test

Updated rules and sampling:

Rule 4: Border only (moved from position 9)
Rule 8: Changed from 3×3 to 4×4 subgrid
Rule 10: Changed from checkerboard to "has cell with 4 neighbors"
Sampling: 40% positive / 25% baseline / 35% round-specific (was 33/33/33)
Variance reduction: 2/1/1 minimum in every 6 rounds (was 3/3/3 in 15)

Test 1: All Rules Have Required Components

Test 2: All Distribution Generators Work

Test 3: Rule Check Functions Work

Test 4: Sample Grids from Each Rule