feat: add multi-engine regex flavour support

src/components/Workbench.test.tsx

@@ -234,6 +234,26 @@ afterEach(() => {
 });
 
 describe("Workbench syntax coordination", () => {
+  it("exposes enumerated engine options and forwards the selected C++ grammar", async () => {
+    vi.useFakeTimers();
+    render(<Workbench />);
+
+    fireEvent.change(screen.getByRole("combobox", { name: "Flavour" }), {
+      target: { value: "cpp" },
+    });
+    const grammar = screen.getByRole("combobox", { name: "Grammar" });
+    expect(grammar).toHaveValue("ECMAScript");
+
+    fireEvent.change(grammar, { target: { value: "extended" } });
+    await advanceParseDebounce();
+
+    expect(syntaxHarness.patterns.at(-1)?.request).toMatchObject({
+      flavour: "cpp",
+      flags: ["g"],
+      options: { grammar: "extended" },
+    });
+  });
+
   it("blocks Run until current syntax arrives and isolates replacement parsing", async () => {
     vi.useFakeTimers();
     render(<Workbench />);