[Python] Release 0.42.0

Fixed

• Panic when validating $ref targets that resolve to boolean schemas.

Performance

• Use FFI PyList_New + PyList_SetItem for array conversion to avoid reallocations.
• Cache ValidationError, ReferencingError, and decimal.Decimal types to avoid repeated module imports.
• Cache formatted schema locations to avoid repeated formatting during evaluate().
• Use as_str instead of to_string for type names in validation errors to avoid allocations.