test(canvas): add KeyboardShortcutsDialog a11y render tests

6 tests covering:
- role=dialog + aria-modal=true
- aria-labelledby pointing to dialog title
- no render when open=false
- Escape calls onClose
- focus moves to close button on open
- Tab is intercepted to trap focus within dialog

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

canvas/src/components/__tests__/KeyboardShortcutsDialog.test.tsx

@@ -0,0 +1,90 @@
+// @vitest-environment jsdom
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { render, screen, fireEvent, cleanup, act, waitFor } from "@testing-library/react";
+
+// ── Component under test — imported AFTER mocks ───────────────────────────────
+import { KeyboardShortcutsDialog } from "../KeyboardShortcutsDialog";
+
+afterEach(cleanup);
+
+const onCloseMock = vi.fn();
+
+beforeEach(() => {
+  onCloseMock.mockReset();
+});
+
+describe("KeyboardShortcutsDialog — a11y render", () => {
+  it("renders with role=dialog and aria-modal=true when open", async () => {
+    render(<KeyboardShortcutsDialog open={true} onClose={onCloseMock} />);
+    await waitFor(() => {
+      expect(screen.getByRole("dialog")).toBeTruthy();
+    });
+    const dialog = screen.getByRole("dialog");
+    expect(dialog.getAttribute("aria-modal")).toBe("true");
+  });
+
+  it("has aria-labelledby pointing to the dialog title", async () => {
+    render(<KeyboardShortcutsDialog open={true} onClose={onCloseMock} />);
+    const dialog = await waitFor(() => screen.getByRole("dialog"));
+    const labelledby = dialog.getAttribute("aria-labelledby");
+    expect(labelledby).toBeTruthy();
+    // The labelledby should reference the h2 with id="keyboard-shortcuts-title"
+    const title = document.getElementById(labelledby!);
+    expect(title?.textContent).toMatch(/keyboard shortcuts/i);
+  });
+
+  it("does not render when open=false", () => {
+    render(<KeyboardShortcutsDialog open={false} onClose={onCloseMock} />);
+    expect(screen.queryByRole("dialog")).toBeNull();
+  });
+
+  it("calls onClose when Escape is pressed", async () => {
+    render(<KeyboardShortcutsDialog open={true} onClose={onCloseMock} />);
+    await waitFor(() => expect(screen.getByRole("dialog")).toBeTruthy());
+    act(() => {
+      fireEvent.keyDown(window, { key: "Escape" });
+    });
+    expect(onCloseMock).toHaveBeenCalledTimes(1);
+  });
+
+  it("focuses the first focusable element (close button) when dialog opens", async () => {
+    render(<KeyboardShortcutsDialog open={true} onClose={onCloseMock} />);
+    // The component uses requestAnimationFrame to move focus; wait for it to settle.
+    await waitFor(() => expect(screen.getByRole("dialog")).toBeTruthy());
+    await act(async () => {
+      await new Promise((r) => requestAnimationFrame(() => requestAnimationFrame(r)));
+    });
+    const closeBtn = screen.getByRole("button", { name: /close/i });
+    expect(document.activeElement).toBe(closeBtn);
+  });
+
+  it("traps Tab focus within the dialog", async () => {
+    render(<KeyboardShortcutsDialog open={true} onClose={onCloseMock} />);
+    const dialog = await waitFor(() => screen.getByRole("dialog"));
+
+    // Collect all focusable elements inside the dialog
+    const focusableSelectors =
+      'button:not([disabled]), [href], input:not([disabled]), select:not([disabled]), textarea:not([disabled]), [tabindex]:not([tabindex="-1"])';
+    const focusableEls = Array.from(
+      dialog.querySelectorAll<HTMLElement>(focusableSelectors)
+    );
+    expect(focusableEls.length).toBeGreaterThan(0);
+
+    const onlyFocusable = focusableEls[0];
+    act(() => { onlyFocusable.focus(); });
+
+    // Simulate Tab keydown. The dialog's handler should call preventDefault()
+    // to stop focus leaving the dialog. Verify by checking the event was
+    // handled (focus remains on the only focusable element).
+    let tabWasIntercepted = false;
+    const tabHandler = (e: KeyboardEvent) => {
+      if (e.key === "Tab") tabWasIntercepted = e.defaultPrevented;
+    };
+    window.addEventListener("keydown", tabHandler);
+    act(() => {
+      fireEvent.keyDown(onlyFocusable, { key: "Tab", shiftKey: false });
+    });
+    expect(tabWasIntercepted).toBe(true);
+    window.removeEventListener("keydown", tabHandler);
+  });
+});