feat(view): colour the ③ 3D rebar by diameter or by member, with a legend

Role colours stay the default (spec §6.7). A control on ③ switches to diameter (nominal size, H and S of one size
share a colour, Okabe–Ito palette) or member (받침블럭 · 코핑 · 기둥 · 확대기초). The legend lists only the items
the model has. Highlighting and the state colours are unchanged. Approved 2026-10-23.

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

src/style.css

@@ -697,3 +697,11 @@ body { background: #eef1f4; font-family: 'Noto Sans KR', system-ui, sans-serif;
 .center-col { flex: 999 1 560px; min-width: 0; display: flex; flex-direction: column; gap: 16px; }
 .center-col > .viewer { flex: none; }
 
+
+/* ③ 3D 색 기준 (spec §6.7): 조작 요소 44px */
+.rebar-color { display: flex; align-items: center; flex-wrap: wrap; gap: 8px; margin: 6px 0; }
+.rebar-color button { min-height: 44px; min-width: 56px; padding: 0 12px; border: 1px solid #b9c4d0; border-radius: 6px; background: #fff; cursor: pointer; }
+.rebar-color button[aria-pressed='true'] { background: #1f5fa8; border-color: #1f5fa8; color: #fff; }
+.rebar-legend { display: flex; flex-wrap: wrap; gap: 10px; list-style: none; margin: 0; padding: 0; font-size: 13px; }
+.rebar-legend-item { display: flex; align-items: center; gap: 6px; }
+.rebar-legend .swatch { display: inline-block; width: 14px; height: 14px; border-radius: 3px; }