feat(render): solid fill for PolyfaceMesh and PolygonMesh entities

PolyfaceMesh and PolygonMesh were wireframe-only. They now render with
the same flat-color solid fill as Face3D entities.

- Add fill_tris: Vec<[f32;3]> to TruckEntity and WireModel
- PolyfaceMesh: fan-triangulate each face into fill_tris
- PolygonMesh: triangulate each grid quad into fill_tris
- tessellate.rs Lines branch: apply world_offset to fill_tris
- Face3DGpu::from_wires: collect fill_tris from all wires in addition
  to Face3D key_vertices quads
- upload_face3d: pass all_wires so fill_tris are batched into one draw call

src/scene/render.rs

@@ -128,7 +128,7 @@ impl shader::Primitive for Primitive {
             pipeline.upload_images(device, queue, &self.images[..]);
             pipeline.upload_meshes(device, &self.meshes[..]);
             pipeline.upload_wires(device, &self.wires[..]);
-            pipeline.upload_face3d(device, &self.face3d_wires[..]);
+            pipeline.upload_face3d(device, &self.face3d_wires[..], &self.wires[..]);
             pipeline.cached_epoch = self.geometry_epoch;
         }
         pipeline.compute_wire_scissors(self.uniforms.view_proj, clip_size.width, clip_size.height);