preprocessing

Shape-based preprocessing for the lesion_calculation v1 step.

This step consumes up to two RAW cached frames: pathology model output (the same frames the GA and fluid calc steps consume) and, optionally, fovea v7 landmark output. preprocess interrogates each frame's shape and applies the matching pipeline; pathology-shaped frames run PATHOLOGY_TO_SEGMENTATION (which preserves mask.instances, the per-label polygons the area masks are built from), and fovea-shaped frames run FOVEA_V7_TO_V6. Unknown shapes pass through unchanged.

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