abutment: X/Z 방향 수정 — 흉벽이 경간에 수직으로 배치

kernel/abutment.rs:
- 흉벽(breast wall): X=횡단(bw_w), Y=높이(bw_h), Z=두께(bw_t) — 올바른 방향
- 기초(footing): X=횡단(ft_w), Y=두께(ft_t), Z=경간방향(ft_l)
- 날개벽(wing wall): ±X 방향으로 연장

viewer/lib.rs: unused imports 제거 (경고 해소)

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

cimery/crates/viewer/src/lib.rs

@@ -24,13 +24,10 @@ use winit::{
     window::{Window, WindowId},
 };
 use wgpu::util::DeviceExt;
-use cimery_core::{MaterialGrade, SectionType};
-use cimery_ir::{FeatureId, GirderIR, PscISectionParams, SectionParams};
 #[cfg(feature = "occt")]
 use cimery_kernel::OcctKernel;
 #[cfg(not(feature = "occt"))]
 use cimery_kernel::PureRustKernel;
-use cimery_kernel::GeomKernel;
 use camera::{Camera, StandardView};
 use glam;