Date picker · calendar select

import { signal } from "./index.js";
import { DatePicker } from "./components/datepicker.js";

const date = signal(null);   // Signal<Date | null>

// a trigger field that opens the Calendar in a popover; closes on pick.
DatePicker({ value: date, placeholder: "Pick a date…",
             format: (d) => d.toLocaleDateString() })