fix(M02): 구조물 설계 컨테이너 미리보기에서 CAD 도구 모음 숨김

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EprXZenk62RAhh6G4v1iEF

M02_MasterTemplete/M02_MasterTemplete_Structure.ts

@@ -122,6 +122,20 @@ export function createStructurePanel(opts: StructurePanelOptions): StructurePane
 
   const note = (text: string): HTMLElement => el("p", { className: "m02-struct__empty", text });
 
+  /** 미리보기 CAD 는 iframe — 안쪽 도구 모음(제목줄 · 리본)을 스타일로 숨김(같은 출처라 접근 가능) */
+  const hideToolbar = (frame: HTMLIFrameElement): void => {
+    const apply = (): void => {
+      const inner = frame.contentDocument;
+      if (!inner?.head || inner.getElementById("m02-struct-hide")) return;
+      const style = inner.createElement("style");
+      style.id = "m02-struct-hide";
+      style.textContent = ".cad-titlebar, .cad-ribbon { display: none !important; }";
+      inner.head.append(style);
+    };
+    frame.addEventListener("load", apply);
+    apply();
+  };
+
   /** 미리보기 · 산출근거 표 — 문서가 없으면 없음 글 */
   const paintBody = (): void => {
     drop();
@@ -141,6 +155,8 @@ export function createStructurePanel(opts: StructurePanelOptions): StructurePane
       name: `preview:${column ?? ""}`,
       layer: "system",
     });
+    const frame = previewHost.querySelector("iframe");
+    if (frame) hideToolbar(frame);
     basis = createSheet(basisHost, doc.산출근거 as unknown as SheetDoc, {
       mode: "master",
       onChange: () => (basisDirty = true),