Function validate_rhs 

pub fn validate_rhs(
    rhs: &[f32],
    expected_len: usize,
) -> Result<(), ValidationError>

Validate a right-hand-side vector for a linear solve.

Checks:

1. rhs.len() == expected_len (dimension must match the matrix).
2. No NaN or Inf entries.
3. If all entries are zero, emits a tracing::warn (a zero RHS is technically valid but often indicates a bug).

Errors

Returns ValidationError on dimension mismatch or non-finite values.