Make quantity trimming direction-aware: DefaultNestEngine uses TrimAxis
(virtual property on NestEngineBase) so HorizontalRemnantEngine removes
topmost parts instead of rightmost. Rename ShrinkAxis.Height → Length
for consistency with Width/Length naming used throughout the codebase.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Two new engine classes subclassing DefaultNestEngine that override
CreateComparer, PreferredDirection, and BuildAngles to optimize for
preserving side remnants. Both registered in NestEngineRegistry and
covered by 6 integration tests.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
