9f27db05

By: Valentin Hirschi <valentin.hirschi@gmail.com>

Contract nonresonant Frobenius solution groups

Combine equal-exponent solution seeds only when the requested recurrence has no positive-order resonance, retaining nonzero log rows and the existing resonant path, domain checks and pivot policy.

Validated with 69 focused/existing tests and a matched PR15 infinity sample: 338 old/new checks at 300 digits and 76 full127 snapshot checks at 200 digits. The single measured infinity phase improved modestly; no whole-workflow speedup is claimed.