fix(poly): typed errors for MultilinearPolynomial TryFrom impls

[vikions]

Replaces type Error = () with a typed MultilinearPolynomialError enum across all 9 TryFrom<&MultilinearPolynomial<F>> implementations, resolving the // TODO(moodlezoup) markers.

Adds MultilinearPolynomialError::WrongVariant { expected, got } with Display and std::error::Error impls, and a private variant_name() helper to report the actual variant on mismatch.

[0xAndoroid]

lgtm, just one nit

[0xAndoroid]

Let's derive the thiserror::Error

Suggested change

	#[derive(Debug, Clone, PartialEq)]
	pub enum MultilinearPolynomialError {
	WrongVariant {
	expected: &'static str,
	got: &'static str,
	},
	}
	impl std::fmt::Display for MultilinearPolynomialError {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
	match self {
	Self::WrongVariant { expected, got } => {
	write!(f, "expected {expected} variant, got {got}")
	}
	}
	}
	}
	impl std::error::Error for MultilinearPolynomialError {}
	#[derive(Error, Debug, Clone, PartialEq)]
	pub enum MultilinearPolynomialError {
	#[error("Invalid MultilinearPolynomial: expected {expected}, got {got}")]
	WrongVariant {
	expected: &'static str,
	got: &'static str,
	},
	}