Determine Whether a Word Transformation Exists

Given a `beginWord`, an `endWord`, and a list of valid words `wordList`, determine whether it is possible to transform `beginWord` into `endWord`. Rules: - Each transformation changes exactly one character. - Every transformed word must exist in `wordList`. - All words contain only lowercase English letters and have the same length. - Return `true` if at least one valid transformation sequence exists; otherwise return `false`. Example: - Input: `beginWord = "hit"`, `endWord = "cog"`, `wordList = ["hot", "dot", "dog", "lot", "log", "cog"]` - Output: `true` Because one valid sequence is: `hit -> hot -> dot -> dog -> cog` You only need to return a boolean value, not the length of the shortest transformation.