test: prove TechLog UI migration parity

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

@@ -360,20 +360,25 @@ describe("TechLog Public not-found runtime", () => {
     ["TECH_LOG_PROJECT_RECORDS" as const, "/projects/missing-project/records"],
     ["TECH_LOG_RELEASE" as const, "/releases/9.9.9"],
     ["TECH_LOG_CASE" as const, "/cases/not-registered"],
-    ["NOT_FOUND" as const, "/definitely-not-a-product-route"],
-  ])("renders exact in-shell Public fallback copy for %s", (routeId, path) => {
+  ])("renders the source-compatible plain fallback for %s", async (routeId, path) => {
     const { container, router } = renderPublicRoute(routeId, path);
 
     expect(router.state.location.pathname).toBe(path);
-    expect(screen.getByRole("heading", { level: 1, name: "404" })).toHaveClass(
-      "next-error-h1",
-    );
-    expect(
-      screen.getByRole("heading", { level: 2, name: "This page could not be found." }),
-    ).toBeVisible();
+    expect(await screen.findByText("Not Found", { exact: true })).toBeVisible();
     expect(
       screen.queryByRole("heading", { name: "화면을 표시하지 못했습니다." }),
     ).not.toBeInTheDocument();
-    expect(container.querySelector(".site-frame")).not.toBeNull();
+    expect(container.querySelector(".site-frame")).toBeNull();
+  });
+
+  it("renders the source-compatible plain fallback for the Public catch-all", () => {
+    const { container, router } = renderPublicRoute(
+      "NOT_FOUND",
+      "/definitely-not-a-product-route",
+    );
+
+    expect(router.state.location.pathname).toBe("/definitely-not-a-product-route");
+    expect(screen.getByText("Not Found", { exact: true })).toBeVisible();
+    expect(container.querySelector(".site-frame")).toBeNull();
   });
 });