fix: normalize role/aria-hidden values — trim + lowercase (Copilot review)

Author: johanrd

lib/rules/template-no-empty-headings.js

@@ -28,7 +28,10 @@ function isAriaHiddenTruthy(attr) {
     return true;
   }
   if (value.type === 'GlimmerTextNode') {
-    const chars = value.chars.toLowerCase();
+    // Normalize like other aria-* value checks: trim incidental whitespace
+    // and compare case-insensitively. `aria-hidden=" true "` is semantically
+    // "true" per the trim step used elsewhere in this rule family.
+    const chars = value.chars.trim().toLowerCase();
     // Empty string is exempted (lean toward fewer false positives).
     return chars === '' || chars === 'true';
   }