bridge_scene: 교대 X 이중 오프셋 수정 — 중심 정렬

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cimery/crates/viewer/src/bridge_scene.rs

@@ -123,7 +123,8 @@ pub fn build_bridge_scene<K: GeomKernel>(kernel: &K) -> Result<Mesh, KernelError
         let mesh = kernel.abutment_mesh(&abut_ir)?;
         // Place abutment: breast wall top at Y = -(BEARING_H)
         let y = -(BEARING_H + abut_ir.breast_wall_height as f32);
-        parts.push(translate(mesh, -(total_w as f32) * 0.5, y, z));
+        // Abutment geometry is already centred at X=0; only Y and Z offset needed.
+        parts.push(translate(mesh, 0.0, y, z));
     }
 
     Ok(merge(parts))