fix: complete TechLog migration evidence

tests/component/router.test.tsx

@@ -343,12 +343,15 @@ describe("generic application router", () => {
     expect(window.location.pathname).toBe("/projects");
   });
 
-  it("renders the source-compatible plain TechLog not-found response", async () => {
+  it("keeps the unreachable client-side Public fallback inside its accessible shell", async () => {
     window.history.pushState({}, "", "/missing");
     renderRouter();
 
-    expect(await screen.findByText("Not Found", { exact: true })).toBeVisible();
-    expect(screen.queryByRole("navigation", { name: "주요 탐색" })).not.toBeInTheDocument();
+    expect(
+      await screen.findByRole("heading", { name: "페이지를 찾을 수 없습니다." }),
+    ).toBeVisible();
+    expect(screen.getByRole("navigation", { name: "주요 탐색" })).toBeVisible();
+    expect(screen.queryByText("Not Found", { exact: true })).not.toBeInTheDocument();
   });
 
   it("keeps Studio routes inside the persistent Studio layout", async () => {