fix(template-no-aria-label-misuse): normalize whitespace and expand static attr detection

- Trim text-node chars in hasNonEmptyLabelAttr so aria-label="   " (whitespace only)
  is treated as empty rather than non-empty.
- Extend getStaticAttrString to return '' for valueless attributes (e.g. <img alt>)
  and return the literal value for mustache string-literal paths (e.g. alt={{""}}),
  so constraint matching for alt="" → presentation role works correctly.

Author: johanrd

lib/rules/template-no-aria-label-misuse.js

@@ -14,10 +14,24 @@ function findAttr(node, name) {
 
 function getStaticAttrString(node, name) {
   const attr = findAttr(node, name);
-  if (!attr || !attr.value || attr.value.type !== 'GlimmerTextNode') {
+  if (!attr) {
     return null;
   }
-  return attr.value.chars;
+  // Valueless attribute (e.g. `<img alt>`) — treat as empty string.
+  if (attr.value === null || attr.value === undefined) {
+    return '';
+  }
+  if (attr.value.type === 'GlimmerTextNode') {
+    return attr.value.chars;
+  }
+  // Mustache with a static string literal path (e.g. `alt={{""}}`).
+  if (
+    attr.value.type === 'GlimmerMustacheStatement' &&
+    attr.value.path?.type === 'GlimmerStringLiteral'
+  ) {
+    return attr.value.path.value;
+  }
+  return null;
 }
 
 // Score how well an elementRoles entry matches the given node. Returns `null`
@@ -139,7 +153,7 @@ function hasNonEmptyLabelAttr(node, name) {
     return false;
   }
   if (attr.value.type === 'GlimmerTextNode') {
-    return attr.value.chars !== '';
+    return attr.value.chars.trim() !== '';
   }
   // Mustache with a static string literal path: `aria-label={{""}}` is still
   // empty, so treat it the same as an empty text node.