Design a hierarchical path registry

Implement an in-memory hierarchical path registry. Support: create(path, value) to create a new path with an integer value and get(path) to return its value or -1 if absent. Constraints: the root '/' exists implicitly; a path can be created only if its parent exists; creating an existing path fails; path segments use lowercase letters and '/' as separator. Describe data structures, APIs, and time/space complexity. Follow-ups: support update and delete (including subtree deletion rules), wildcard queries, and watch callbacks that trigger on changes to a path or subtree.