Merge PR #300: tessellate hatch fills so navigation no longer flickers (#258)

External contribution by sLuCHa. Triangulates each hatch boundary once
(lyon even-odd, cached with the batch build) and rasterizes the triangles
instead of the per-fragment point-in-polygon test, removing the screen-fill
overdraw + boundary raycast that forced the flicker-causing interaction LOD
(now default off behind OCS_HATCH_LOD). Precision preserved (triangles in the
same world_origin-relative frame + RTE path); untessellatable boundaries fall
back to the old AABB-quad + in_polygon path (poly_test=1).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/scene/pipeline/mod.rs

@@ -1,5 +1,6 @@
 pub mod face3d_gpu;
 pub mod hatch_batched_gpu;
+pub mod hatch_tess;
 pub mod hatch_gpu;
 pub mod image_gpu;
 pub mod mesh_gpu;