タグ “廃止” 追加 (#378) (#379)

Reviewed-on: #379
Co-authored-by: miteruzo <miteruzo@naver.com>
Co-committed-by: miteruzo <miteruzo@naver.com>

frontend/src/pages/wiki/WikiDiffPage.test.tsx

@@ -16,6 +16,7 @@ describe ('WikiDiffPage', () => {
     api.apiGet.mockResolvedValueOnce ({
       wikiPageId:      3,
       title:           '差分対象',
+      deprecatedAt:    null,
       olderRevisionId: 1,
       newerRevisionId: 2,
       diff: [
@@ -43,4 +44,26 @@ describe ('WikiDiffPage', () => {
     expect (screen.getByText ('added line')).toBeInTheDocument ()
     expect (screen.getByText ('removed line')).toBeInTheDocument ()
   })
+
+  it ('appends deprecated state to the wiki title', async () => {
+    api.apiGet.mockResolvedValueOnce ({
+      wikiPageId:      3,
+      title:           '廃止 Wiki',
+      deprecatedAt:    '2026-06-01T00:00:00.000Z',
+      olderRevisionId: 1,
+      newerRevisionId: 2,
+      diff:            [],
+    })
+
+    renderWithProviders (
+        <Routes>
+          <Route path="/wiki/:id/diff" element={<WikiDiffPage/>}/>
+        </Routes>,
+        { route: '/wiki/3/diff?from=1&to=2' },
+    )
+
+    expect (await screen.findByRole ('heading', {
+      name: '廃止 Wiki（廃止）',
+    })).toBeInTheDocument ()
+  })
 })