Run the top bar's colour up behind the Dynamic Island on iOS 26 (#147)

46f9370 set theme-color, but Safari 26 ignores it. iOS 26 paints the strip behind the status bar
and the island in the background colour of a sticky or fixed element at the page's top edge, and
failing that the root's. The top bar was neither, and the root had no colour of its own (only
body did), so iOS used black or white: a band of another colour above the bar.

The bar is sticky now, though nothing scrolls under it, so iOS reads its colour; the root has the
page's background for screens with nothing at the top edge; Classic's metal bar gets a colour
under its gradient, the top of the metal, since iOS reads no gradient. theme-color stays, set to
the bar's colour, for iPhones before iOS 26 and for Android. Glass's bar is see-through, so iOS
frosts what is under it there, as the bar itself does.

Taken from developers' reports of iOS 26, not Apple's documentation, and not yet seen on a phone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/ui/app.spec.js

@@ -1667,9 +1667,11 @@ test.describe('on a narrow phone', () => {
     const tops = await page.locator('#content .acts .btn').evaluateAll(bs => bs.map(b => b.getBoundingClientRect().top));
     expect(tops.length).toBe(7);
     expect(new Set(tops).size).toBe(1);
-    // iOS paints the status bar round the Dynamic Island in theme-color, its own black or white
-    // without one (#147).
-    expect(await page.evaluate(() => document.querySelector('meta[name=theme-color]').content))
-      .toBe(await page.evaluate(() => getComputedStyle(document.body).backgroundColor));
+    // iOS 26 paints behind the status bar and the Dynamic Island in the colour of a sticky bar at
+    // the top edge, older ones in theme-color: both the top bar's, which is the page's (#147).
+    const bar = await page.locator('#topbar').evaluate(b => [getComputedStyle(b).position, b.getBoundingClientRect().top, getComputedStyle(b).backgroundColor]);
+    expect(bar.slice(0, 2)).toEqual(['sticky', 0]);
+    expect(bar[2]).toBe(await page.evaluate(() => getComputedStyle(document.body).backgroundColor));
+    expect(await page.evaluate(() => document.querySelector('meta[name=theme-color]').content)).toBe(bar[2]);
   });
 });