HandleId duplicated ImageHandle with conversion tables both ways; the
image engine now takes ImageHandle, which also carries the cursor icon,
and the crop grips map through one GRIPS table instead of two index
matches. ImageObb loses from_center_size_angle, scale_proportional,
project_delta, new, handle_id, handles_with_ids and the width, height
and theta fields, which only the test of scale_proportional read.
reset_crop, RESIZE_ACCENT, image_owns_pointer and DragTarget::CropHandle
had no callers, and turn_degrees is test-only. The image engine is
private and its unused re-exports are gone.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>