test(e2e): freeze the context menu's keyboard model

Two of the three things that made it work are invisible to a component
test against hand-built markup: the real wa-dropdown-items have not set
their role when the host finishes updating, and the real wa-popup has
not positioned itself, so focus() on an item is a silent no-op. Both
produced a menu that opened and refused to take focus.

e2e/specs/menu-keyboard.spec.ts

@@ -0,0 +1,125 @@
+import { test, expect } from '../support/fixtures.js';
+
+/**
+ * The context menu is reachable, navigable and escapable without a
+ * mouse.
+ *
+ * `a11y.3`: the menu is the only route to Play, Add to Queue, Play Next,
+ * Add to Playlist, Favourite and Track Details, and it opened on
+ * `contextmenu` alone. The panel had no `role="menu"`, so the six
+ * `role="menuitem"`s Web Awesome sets were orphaned; nothing moved focus
+ * into it, nothing handled Arrow or Escape, and nothing restored focus.
+ *
+ * Frozen here because two of the three things that made it work are
+ * invisible to a component test running against hand-built markup: the
+ * real `wa-dropdown-item`s do not have their `role` yet when the host
+ * finishes updating, and the real `wa-popup` has not positioned itself,
+ * so `focus()` on an item is a silent no-op. Both produced a menu that
+ * opened and refused to take focus, which is exactly the bug this spec
+ * exists to catch.
+ */
+test.describe('the context menu without a mouse', () => {
+  /** The deep-focused element, described the way an AT would see it. */
+  const focused = (page: import('@playwright/test').Page) =>
+    page.evaluate(() => {
+      let el = document.activeElement;
+
+      while (el?.shadowRoot?.activeElement) el = el.shadowRoot.activeElement;
+
+      return {
+        role: el?.getAttribute('role') ?? '',
+        text: el?.textContent?.trim().slice(0, 40) ?? '',
+      };
+    });
+
+  /** The menu panel's own semantics, or null when it is not rendered. */
+  const panel = (page: import('@playwright/test').Page) =>
+    page.evaluate(() => {
+      const el = document
+        .querySelector('track-list')
+        ?.shadowRoot?.querySelector('.context-menu-panel');
+
+      if (!el) return null;
+
+      return {
+        role: el.getAttribute('role'),
+        label: el.getAttribute('aria-label'),
+        items: el.querySelectorAll('[role="menuitem"]').length,
+      };
+    });
+
+  /** Tab to the track list's single roving stop. */
+  async function focusARow(app: import('@playwright/test').Page) {
+    for (let i = 0; i < 25; i += 1) {
+      await app.keyboard.press('Tab');
+
+      if ((await focused(app)).role === 'row') return;
+    }
+
+    throw new Error('never reached a track row');
+  }
+
+  test.beforeEach(async ({ app }) => {
+    await app.getByTestId('nav-tracks').click();
+    await expect(app.getByTestId('main-content')).toHaveAttribute(
+      'data-active-view',
+      'tracks',
+    );
+  });
+
+  test('Shift+F10 on a row opens a menu and focuses its first item', async ({
+    app,
+  }) => {
+    await focusARow(app);
+    await app.keyboard.press('Shift+F10');
+
+    await expect.poll(() => panel(app)).toMatchObject({
+      role: 'menu',
+      label: 'Track actions',
+    });
+
+    // The row is where the key came from; the menu is where focus went.
+    await expect.poll(async () => (await focused(app)).role).toBe('menuitem');
+  });
+
+  test('the arrows move through the items and wrap', async ({ app }) => {
+    await focusARow(app);
+    await app.keyboard.press('Shift+F10');
+    await expect.poll(async () => (await focused(app)).role).toBe('menuitem');
+
+    const first = (await focused(app)).text;
+
+    await app.keyboard.press('ArrowDown');
+
+    const second = (await focused(app)).text;
+
+    expect(second).not.toBe(first);
+
+    await app.keyboard.press('ArrowUp');
+    expect((await focused(app)).text).toBe(first);
+
+    // Up from the first item wraps to the last, which is what a menu
+    // does and what a list does not.
+    await app.keyboard.press('ArrowUp');
+    expect((await focused(app)).text).not.toBe(first);
+
+    await app.keyboard.press('Escape');
+  });
+
+  test('Escape closes the menu and gives the row its focus back', async ({
+    app,
+  }) => {
+    await focusARow(app);
+
+    const row = (await focused(app)).text;
+
+    await app.keyboard.press('Shift+F10');
+    await expect.poll(async () => (await focused(app)).role).toBe('menuitem');
+
+    await app.keyboard.press('Escape');
+
+    await expect.poll(() => panel(app)).toBeNull();
+    await expect.poll(async () => (await focused(app)).role).toBe('row');
+    expect((await focused(app)).text).toBe(row);
+  });
+});