Removes cql_grad_scratch_ptr, iqn_trunk_m_ptr, save_h_s1_ptr,
stream_cu — added during NaN investigation, no longer called.
Retains run_nan_tracing (lightweight GPU-side checks on first 20 steps)
and all isfinite guards as production safety nets.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>