Read Nested Data with a Dotted Path

API responses and LLM tool outputs are deeply nested JSON. Write a safe accessor: get_path(data, "user.addresses.0.city", default=None).

• Split the path on .. For dicts, look up the key. For lists, the segment must be an integer index (negative indices allowed).
• If anything along the way is missing, out of range or the wrong type, return default instead of raising.
• An empty path returns data itself.

Then implement set_path(data, path, value), which sets a value and creates missing dicts along the way. Numeric segments into existing lists set by index. set_path modifies data in place and returns it.