Fresh `pip install pycardano` is broken: cbor2 6.x removed CBORDecodeValueError

[pmcorcoran]

Describe the bug
cbor2 6.0.0 removed CBORDecodeValueError as a
backward-incompatible change. pyproject.toml declares cbor2 = ">=5.6.5" , so pip installs 6.x alongside a cbor2pure that still imports the 5.x name.

To Reproduce
clean venv, Python 3.12, pip install pycardano, then import pycardano.

Logs
Resolves to pycardano 0.19.2, cbor2 6.1.3, cbor2pure 5.8.0, and raises:

File "/.venv/lib/python3.12/site-packages/cbor2pure/init.py", line 6, in
from cbor2 import CBORDecodeValueError as CBORDecodeValueError
ImportError: cannot import name 'CBORDecodeValueError' from 'cbor2' (/.venv/lib/python3.12/site-packages/cbor2/init.py). Did you mean: 'CBOREncodeValueError'?

Environment and software version (please complete the following information):

• OS: Ubuntu 24.04.4 LTS
• PyCardano Version 0.19.2
• Python version 3.12