Part.Clone and CloneAtOffset copied the lead-in program but not
HasManualLeadIns, LeadInsLocked, CuttingParameters or the tracked
pre-lead-in rotation. A copy of a rotated lead-in part reported
rotation 0 (the rebuilt program's), so saving it wrote the wrong
rotation and Remove Lead-ins restored an unrotated part.
Part.Rotate on a lead-in part set the tracked rotation from the
lead-in program's own Rotation, which starts at zero when the cutting
strategy rebuilds it, so a further quarter turn left Rotation unchanged.
Lead-in parts now accumulate the applied angle instead.
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