Implements two IFillComparer strategies that preserve axis-aligned remnants:
VerticalRemnantComparer minimizes X-extent, HorizontalRemnantComparer minimizes
Y-extent, both using a count > extent > density tiebreak chain. Includes 12
unit tests covering all tiebreak levels and null-guard cases.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Extracts the fill result scoring contract into IFillComparer with a DefaultFillComparer implementation that preserves the existing count-then-density lexicographic ranking via FillScore.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
