Replace the small QCAD CXF stroke-font set with the full LibreCAD LFF font
library (46 fonts) and a new LFF parser/engine in src/scene/lff.rs. The
parser reads the `[hex] char` glyph blocks, tessellates `,A<bulge>` arcs, and
resolves `C<hex>` glyph references. Per LibreCAD's RS_Polyline convention a
vertex's bulge curves the segment ending at that vertex — getting this wrong
turned round letters like O into sideways capsules.
Font name resolution mirrors LibreCAD: match by file stem, map common
AutoCAD/DXF SHX names (txt, isocp, complex, italic, gothic*, gost, …) to the
nearest LFF family, and fall back to `standard`. A missing glyph in the chosen
family falls back to the broad `unicode` font so accented/Cyrillic/Greek text
still renders. Cap height stays 9 units, so the text scale is unchanged.
All text consumers move from cxf:: to lff::; complex linetypes still render
embedded text but no longer draw embedded shapes (LibreCAD ships no shape
file). The CXF module and every *.cxf asset are removed, and the MText / text
style font pickers list the LFF families.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
