Validate characters in potential enum values

Added regex check to ensure the value only contains valid Java identifier
characters (letters, digits, underscores, dollar signs, and dots). Values
containing spaces, quotes, or other special characters are not valid enum
references.

Author: Jenson3210

rewrite-java/src/main/java/org/openrewrite/java/AddOrUpdateAnnotationAttribute.java

@@ -292,19 +292,12 @@ private static String getFullyQualifiedClass(String fqn) {
     }
 
     private boolean isFullyQualifiedEnumValue(J.Annotation annotation) {
-        // A fully qualified enum value has at least 2 dots in a single value: package.EnumClass.CONSTANT
-        // e.g., org.example.Values.ONE
-        // We check that the enum class portion (everything before the last dot) itself contains a dot
-        // Also verify the attribute type is not a String to avoid treating "some.dotted.string" as an enum
         if (attributeValue == null || attributeValue.endsWith(".class") || attributeValue.contains(",")) {
             return false;
         }
-        // Require type information to safely determine if this is an enum value
-        // Without type info, we can't distinguish between a dotted string and an enum reference
-        if (!findMethod(annotation, attributeName()).isPresent()) {
-            return false;
-        }
-        if (attributeIsString(annotation)) {
+        if (!attributeValue.matches("[\\w.$]+") ||
+            !findMethod(annotation, attributeName()).isPresent() ||
+            attributeIsString(annotation)) {
             return false;
         }
         int lastDot = attributeValue.lastIndexOf('.');