Preserve narrow spline clearances when tessellating solid fills

Recover failed small spline boundaries with the kernel chord-error
sampler, using the same coordinate frame as the fill mesh. Preserve
source curves and enforce recovery and total hatch vertex limits.

Fixes #1268

src/scene/mod.rs

@@ -33,6 +33,7 @@ pub(crate) mod dimension_assoc;
 pub(crate) mod centermark;
 mod dwg_native_constraints;
 mod entity;
+mod hatch_boundary;
 mod group_layer;
 mod layout;
 mod limits;