Revert "fix: skip degenerate triangle for 3-corner Face3D"

This reverts commit 517af91245.

src/scene/pipeline/face3d_gpu.rs

@@ -69,21 +69,14 @@ impl Face3DGpu {
             let p = &wire.key_vertices;
             let v = |i: usize| Face3DVertex { position: p[i], color };
 
-            let dx = p[3][0] - p[2][0];
-            let dy = p[3][1] - p[2][1];
-            let dz = p[3][2] - p[2][2];
-            let is_triangle = dx * dx + dy * dy + dz * dz < 1e-10;
-
             // Triangle 1: p0, p1, p2
             vertices.push(v(0));
             vertices.push(v(1));
             vertices.push(v(2));
-            // Triangle 2 only for quads (triangles have p3 == p2).
-            if !is_triangle {
-                vertices.push(v(0));
-                vertices.push(v(2));
-                vertices.push(v(3));
-            }
+            // Triangle 2: p0, p2, p3
+            vertices.push(v(0));
+            vertices.push(v(2));
+            vertices.push(v(3));
         }
 
         let vertex_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {