fix: trim static attr value, remove dead code (Copilot review)

- getStaticAttrValue() now trims chars so callers don't handle whitespace.
- Lowercase the node value when comparing against aria-query's attrSpec.value
  (HTML enumerated attribute values are ASCII case-insensitive per HTML
  common-microsyntaxes §2.3.3).
- Remove unused createUnsupportedAttributeErrorMessage() dead code; the rule
  uses messageId/data exclusively.

Author: johanrd

lib/rules/template-no-unsupported-role-attributes.js

@@ -1,13 +1,5 @@
 const { roles, elementRoles } = require('aria-query');
 
-function createUnsupportedAttributeErrorMessage(attribute, role, element) {
-  if (element) {
-    return `The attribute ${attribute} is not supported by the element ${element} with the implicit role of ${role}`;
-  }
-
-  return `The attribute ${attribute} is not supported by the role ${role}`;
-}
-
 function getStaticAttrValue(node, name) {
   const attr = node.attributes?.find((a) => a.name === name);
   if (!attr) {
@@ -17,7 +9,7 @@ function getStaticAttrValue(node, name) {
     // Presence with dynamic value — treat as "set" but unknown string.
     return '';
   }
-  return attr.value.chars;
+  return attr.value.chars.trim();
 }
 
 function nodeSatisfiesAttributeConstraint(node, attrSpec) {
@@ -31,7 +23,10 @@ function nodeSatisfiesAttributeConstraint(node, attrSpec) {
     return !isSet;
   }
   if (attrSpec.value !== undefined) {
-    return isSet && value === attrSpec.value;
+    // HTML enumerated attribute values are ASCII case-insensitive
+    // (HTML common-microsyntaxes §2.3.3). aria-query's attrSpec.value is
+    // already lowercase, so lowercase the node's value for comparison.
+    return isSet && value.toLowerCase() === attrSpec.value;
   }
   // No constraint listed — just require presence.
   return isSet;