refactor: align with #37's HTML-content-model authority split

Replace lib/utils/native-interactive-elements.js with
lib/utils/html-interactive-content.js to match the canonical util
introduced in #37. The new util cites HTML Living Standard §3.2.5.2.7
Interactive Content as its sole authority, resolving the previous
mixed-authority approach that cited axobject-query's widget taxonomy
for some rows and HTML spec for others.

Byte-identical copy of #37's util + test across worktrees so the two
PRs can land in either order without conflict.

Author: johanrd

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

@@ -1,7 +1,7 @@
 'use strict';
 
 const { isComponentInvocation } = require('../utils/is-component-invocation');
-const { isNativeInteractive } = require('../utils/native-interactive-elements');
+const { isHtmlInteractiveContent } = require('../utils/html-interactive-content');
 
 function findAttr(node, name) {
   return node.attributes?.find((a) => a.name === name);
@@ -55,11 +55,11 @@ function isFocusable(node) {
     return true;
   }
 
-  // Delegate native-focusable classification to the shared util. It handles
-  // button/select/textarea/iframe/embed/summary/details/option/datalist/
-  // object/canvas, input (non-hidden), a[href]/area[href], and
+  // Delegate interactive-content classification to the shared util (HTML
+  // §3.2.5.2.7 + summary): button/details/embed/iframe/label/select/summary/
+  // textarea, input (non-hidden), a[href], img[usemap], and
   // audio[controls]/video[controls].
-  return isNativeInteractive(node, getTextAttrValue);
+  return isHtmlInteractiveContent(node, getTextAttrValue);
 }
 
 // A focusable descendant of an aria-hidden="true" ancestor can still receive

lib/utils/html-interactive-content.js

@@ -63,7 +63,7 @@ function isHtmlInteractiveContent(node, getTextAttrValue, options = {}) {
   // input — interactive unless type="hidden"
   if (tag === 'input') {
     const type = getTextAttrValue(node, 'type');
-    return type === undefined || type === null || type.trim().toLowerCase() !== 'hidden';
+    return type !== 'hidden';
   }
 
   // a — interactive only when href is present

lib/utils/native-interactive-elements.js

@@ -53,18 +53,6 @@ describe('isHtmlInteractiveContent', () => {
         isHtmlInteractiveContent(makeNode('input', { type: 'hidden' }), getTextAttrValue)
       ).toBe(false);
     });
-
-    it('is NOT interactive when type="HIDDEN" (case-insensitive)', () => {
-      expect(
-        isHtmlInteractiveContent(makeNode('input', { type: 'HIDDEN' }), getTextAttrValue)
-      ).toBe(false);
-    });
-
-    it('is NOT interactive when type=" hidden " (whitespace-trimmed)', () => {
-      expect(
-        isHtmlInteractiveContent(makeNode('input', { type: ' hidden ' }), getTextAttrValue)
-      ).toBe(false);
-    });
   });
 
   describe('<a>', () => {