feat(view): ③ rebar view at 50% for members, ground and blinding; deeper rebar colour

On ③ the members, the ground and the blinding concrete are drawn at half opacity without depth writes, so the bars show
through. Outside ③ each part returns to its own opacity. Rebar colours are shaded to 0.8 and slightly glossier so they
read through the members. Approved 2026-10-23.

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

src/view/rebar3d.ts

@@ -33,6 +33,9 @@ const OTHER_COLOR = 0x8c8c8c;
 const MEMBER_COLORS: Record<RebarMemberKey, number> = { bearing: 0xe69f00, coping: 0x0072b2, column: 0x009e73, footing: 0xcc79a7, other: OTHER_COLOR };
 const MEMBER_LABELS: Record<RebarMemberKey, string> = { bearing: '받침블럭', coping: '코핑', column: '기둥', footing: '확대기초', other: '기타' };
 const hex = (v: number) => `#${v.toString(16).padStart(6, '0')}`;
+/** Rebar is drawn a little deeper than the 6.7 colours so it reads through the half-transparent members (승인 2026-10-23). */
+const REBAR_SHADE = 0.8;
+const rebarColor = (v: number) => new THREE.Color(v).multiplyScalar(REBAR_SHADE);
 
 const COLOR = {
   coping: 0xb4531f,
@@ -66,7 +69,7 @@ export function buildRebar3D(m: PierModel, common: Material = DEFAULT_MATERIAL,
     geo.applyQuaternion(new THREE.Quaternion().setFromUnitVectors(new THREE.Vector3(0, 1, 0), dir.normalize()));
     geo.translate((a[0] + b[0]) / 2, (a[1] + b[1]) / 2, (a[2] + b[2]) / 2);
     geo.applyMatrix4(Ms[k]);
-    const mat = new THREE.MeshStandardMaterial({ color, roughness: 0.6, metalness: 0.1 });
+    const mat = new THREE.MeshStandardMaterial({ color: rebarColor(color), roughness: 0.45, metalness: 0.1 });
     const mesh = new THREE.Mesh(geo, mat);
     mesh.userData = { name, roleColor: color, dMm, member: memberOfBar(name) };
     group.add(mesh);
@@ -459,7 +462,7 @@ export function buildRebar3D(m: PierModel, common: Material = DEFAULT_MATERIAL,
   };
   const setColorMode = (mode: RebarColorMode) => {
     for (const meshes of byName.values()) {
-      for (const mesh of meshes) (mesh.material as THREE.MeshStandardMaterial).color.setHex(colorOf(mesh, mode));
+      for (const mesh of meshes) (mesh.material as THREE.MeshStandardMaterial).color.copy(rebarColor(colorOf(mesh, mode)));
     }
   };
   const legend = (mode: RebarColorMode) => {