fix(#19): drop details/option/datalist from focusable set (Copilot review)

Per HTML §6.6.3 'Sequential focus navigation', none of <details>,
<option>, or <datalist> are focusable by default:
- <details>: the focusable control is its <summary> child
- <option>: not in default tab order; <select> is focused and arrow keys
  navigate options within it
- <datalist>: no user-facing UI; the paired <input list> is focused

Including them in UNCONDITIONAL_FOCUSABLE_TAGS was over-aggressive and
caused false positives on this rule. Tests updated to pin the
now-allowed cases.

Author: johanrd

lib/rules/template-no-aria-hidden-on-focusable.js

@@ -44,16 +44,19 @@ function isAriaHiddenTrue(node) {
 // focusable by default — clicks on a label forward to its associated control,
 // but the label itself isn't in the tab order. So it's excluded here even
 // though `isHtmlInteractiveContent` would return true for it.
+// Per HTML §6.6.3 "Sequential focus navigation", tags in the default tab
+// order without further qualification. Explicitly excluded:
+//   - <details>: the focusable control is its <summary> child, not details.
+//   - <option>: not in the default focus order; <select> is focused and
+//     arrow keys navigate options within it (not Tab).
+//   - <datalist>: no user-facing UI; the paired <input list> is focused.
 const UNCONDITIONAL_FOCUSABLE_TAGS = new Set([
   'button',
   'select',
   'textarea',
   'iframe',
   'embed',
   'summary',
-  'details',
-  'option',
-  'datalist',
 ]);
 
 // Form-control tags whose `disabled` attribute removes them from the tab order