DrawingSplitter now clips bend lines to each piece's region using
Liang-Barsky line clipping and offsets them to the new origin. Bend
properties (direction, angle, radius, note text) are preserved through
the entire split pipeline instead of being lost during re-import.
CadConverterForm applies the same origin offset to bends before passing
them to the splitter, and creates FileListItems directly from split
results to avoid re-detection overwriting the bend metadata.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>