fix(m02): 상세 이동 단추 테두리 꼴 — 눌림 글이 안 보이던 것(105-4)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015KYZ2HWWdUwZWYnn3tQz7X

M02_MasterTemplete/M02_MasterTemplete_DetailNav.ts

@@ -32,7 +32,7 @@ export interface DetailNav {
 
 export function createDetailNav(go: (kind: DetailKind) => void): DetailNav {
   const buttons = ITEMS.map(([kind, label]) => {
-    const button = createButton({ label, size: "sm", onClick: () => go(kind) });
+    const button = createButton({ label, size: "sm", variant: "ghost", onClick: () => go(kind) });
     button.dataset.detailNav = kind;
     return button;
   });