[Python] Release 0.42.2

Fixed

• SWAR digit parser accepted bytes :–? (0x3A–0x3F) as valid digits during date, time, and date-time format validation, potentially allowing malformed values to pass.

Changed

• Custom keyword validation exceptions are now chained to the resulting ValidationError via __cause__, preserving the original exception type and message.

Performance

• Extend pattern prefix optimization to handle escaped slashes (^\/) and exact-match patterns (^\$ref$).
• Specialize enum for cases when all variants are strings.