EditDrawingsInConverter was replacing Drawing objects with new instances,
but Part.BaseDrawing is readonly — parts kept referencing the old drawings
with stale programs (e.g. etch lines that were removed). Now matches by
name and updates existing drawings in-place, then refreshes all parts.
Also fixes Part.Update() which applied rotation backwards and was missing
UpdateBounds() and lead-in state reset.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>