Implement trie-based autocomplete

## Problem Design an autocomplete data structure using a **trie**. You must support: 1. `insert(word: string) -> void` 2. `search(word: string) -> bool` (exact match) 3. `startsWith(prefix: string) -> bool` 4. `suggest(prefix: string, limit: int) -> list[string]` returning up to `limit` words that start with `prefix`. ## Notes / Constraints - Words contain lowercase English letters `a-z`. - `suggest` may return results in any deterministic order (e.g., lexicographic) as long as it is consistent. - Aim for typical trie complexities: O(L) for insert/search where L is string length; `suggest` should be proportional to output size (plus traversal). ## Edge cases - Duplicate inserts. - Empty prefix. - Prefix that matches no words.