Add optional vector diagram export pipeline for publication-quality SVG/PDF output

Add optional vector diagram export pipeline for publication-quality SVG/PDF output: a task in LegoFlow-SWE (Harbor dataset). Problem Currently, methodology diagrams are only produced as raster images (PNG/JPEG/WebP). This limits publication workflows that require scalable line art, such as SVG or…

The task

**Problem** Currently, methodology diagrams are only produced as raster images (PNG/JPEG/WebP). This limits publication workflows that require scalable line art, such as SVG or PDF for print-quality figures and editable graphics. Researchers need a way to obtain vector versions of the automatically generated diagrams.

Part of Lego-X/LegoFlow-SWE.