datepicker: ui-datepicker-div always visible after init

Versions:

• jQuery 3.6.1
• jquery ui 1.13.2

Prerequisites:

• css applied:
  .ui-datepicker { border: 1px solid #ccc; padding: 6px;

Reproduction path:

• Initialize datepicker on input field

Expected behavior:

• .ui-datepicker div is not visible

Current behavior:

• .ui-datepicker div is visible, causing a small box to appear at the bottom of the page

Discussion:

• The div is only visible after initialization and before the first time showing the widget. After hiding the widget, datepicker applies style display: none to the div.
• This can't be fixed by adding display: none to the class ourselves, because the code to show the widget does not apply a different display value in-line. It just removes the display: none inline style. Thus, applying display: none in our css results in the widget never being shown.
• My conclusion: jquery-ui should set display: none on initialisation.

Reproduce the datepicker initialization described in the issue with the listed jQuery and jQuery UI versions, then inspect the datepicker initialization and show/hide behavior. Done means the widget is hidden after initialization, remains usable when first shown, and still hides correctly afterward.