gkrgates: fix VerifyDegree error wrapping and degree search bound

[ANtutov]

Wrap the original verification error instead of the finder error to preserve context in diagnostics.
Use a sensible max bound (32) when inferring degree for diagnostics, aligned with Register.
Improves error messages (“detected degree X …”) and avoids false negatives when the claimed degree is too low.

[ivokub]

@Tabaie - seems legit. Can you confirm that the default max degree makes sense?