Function enforce_load_contract 

pub fn enforce_load_contract(
    apr_name: &str,
    apr_shape: &[usize],
    vocab_size: usize,
    hidden_dim: usize,
) -> Result<(), ContractError>

MANDATORY: Validate tensor shape during APR model load.

This function MUST be called when loading tensors from APR format. It validates that the shape matches the contract expectation.

Errors

Returns Err if the shape violates the contract. Callers MUST propagate this error - do not ignore it.