Add full shell, replaceable Omics adapter and bilingual interaction

Implement approved specification #32 and tickets #33-#37. Keep host authentication server-verified and pin session interaction language. Compile scoped base selectors for browser compatibility and retain full gutters during CSS pruning.

frontend/src/widgets/FallbackWidget.test.tsx

@@ -0,0 +1,27 @@
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { FallbackWidget } from "./FallbackWidget";
+
+function reloadIsBlocked() {
+  const event = new Event("beforeunload", { cancelable: true });
+  window.dispatchEvent(event);
+  return event.defaultPrevented;
+}
+
+test("protects manual response drafts until cleared or unmounted, including after sending", async () => {
+  const onRespond = vi.fn();
+  const { unmount } = render(<FallbackWidget descriptor={{ id: "unknown", widget: "unknown" }} onRespond={onRespond} />);
+  expect(reloadIsBlocked()).toBe(false);
+  await userEvent.type(screen.getByRole("textbox"), "Manual answer");
+  expect(reloadIsBlocked()).toBe(true);
+  await userEvent.clear(screen.getByRole("textbox"));
+  expect(reloadIsBlocked()).toBe(false);
+  await userEvent.type(screen.getByRole("textbox"), "Correction");
+  await userEvent.click(screen.getByRole("button", { name: "Send" }));
+  expect(onRespond).toHaveBeenCalledWith({ id: "unknown", control: "freetext", text: "Correction" });
+  expect(reloadIsBlocked()).toBe(true);
+  await userEvent.type(screen.getByRole("textbox"), " updated");
+  expect(reloadIsBlocked()).toBe(true);
+  unmount();
+  expect(reloadIsBlocked()).toBe(false);
+});