This new system is a "Work in Progress"

const stream = openSaveFileStream("example.txt", "text/plain");

const writer = stream.getWriter();

await writer.write(new TextEncoder().encode("Hello "));
await writer.write(new TextEncoder().encode("World"));

await writer.close();

#extra-keys {
  background: #1a1a1a;
  border-top: 1px solid #333;
  padding: 8px;
  padding-bottom: calc(var(--window-keyboard-height, var(--window-inset-bottom, 0px)) + 8px) !important;
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  justify-content: space-around;
  min-height: 44px;
  box-sizing: border-box;
  flex-shrink: 0;
  transition: transform 0.3s ease, opacity 0.3s ease;
}