fix(rebar): pass the ③ material to C15/C16, coping bottom and column bars

The stair bars in the 철근표 and the 3D model, and the 3D bottom and column bars, were built with the default fck,
so a changed fck did not reach them. buildRebar3D now takes the material, and a material change rebuilds the scene.

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

src/main.ts

@@ -225,7 +225,7 @@ function setupScene(): void {
   rebar3d = null;
   const pier = activePier();
   if (pier?.model) {
-    rebar3d = buildRebar3D(pier.model);
+    rebar3d = buildRebar3D(pier.model, state.material);
     rebar3d.group.visible = state.stage === 'rebar';
     world.add(rebar3d.group);
     const scene = buildPierScene(pier.model);
@@ -926,6 +926,8 @@ function setMaterial(key: keyof Material, raw: string): void {
     return;
   }
   state.material = { ...state.material, [key]: value };
+  // The 3D bars depend on the material too (their lengths), so the scene is rebuilt with it.
+  setupScene();
   renderAll();
 }