fix: complete TechLog migration evidence

tests/features/tech-log/public-document-screens.test.tsx

@@ -337,12 +337,14 @@ describe("TechLog topics and Public not-found routing", () => {
     ["TECH_LOG_REFERENCE" as const, "/references/not-registered"],
     ["TECH_LOG_QUESTION" as const, "/questions/not-registered"],
     ["TECH_LOG_TOPIC" as const, "/topics/not-registered"],
-  ])("uses the source production plain 404 for %s", async (routeId, path) => {
+  ])("keeps the unreachable client fallback accessible for %s", async (routeId, path) => {
     const { container, router } = renderDocumentRoute(routeId, path);
 
     expect(router.state.location.pathname).toBe(path);
-    expect(await screen.findByText("Not Found", { exact: true })).toBeVisible();
+    expect(
+      await screen.findByRole("heading", { name: "페이지를 찾을 수 없습니다." }),
+    ).toBeVisible();
     expect(screen.queryByRole("heading", { name: "화면을 표시하지 못했습니다." })).not.toBeInTheDocument();
-    expect(container.querySelector(".site-frame")).toBeNull();
+    expect(container.querySelector(".site-frame")).not.toBeNull();
   });
 });