Function validate_type_specifications 

pub fn validate_type_specifications(
    specs: &TypeSpecification,
    type_name: &str,
    source: &Source,
) -> Vec<LemmaError>

Validate that TypeSpecification constraints are internally consistent

This checks:

• minimum <= maximum (for types that support ranges)
• default values satisfy all constraints
• length constraints are consistent (for Text)
• precision/decimals are within valid ranges

Returns a vector of errors (empty if valid)