Two refinements from measuring the first rotated re-cuts of the real kits:

1. Junction in the pre-attack pocket. The rotation point was zc-snapped
   ±symmetrically around the downbeat, which could land the loop wrap
   mid-transient (rotated hammer drums read seam 0.50 / click_db −0.03:
   physically continuous, but the junction sat in busy material and a
   re-trigger clipped into the groove). _pocket_zc() searches
   [−25 ms, +2 ms] around the target and picks the zero crossing with
   the smallest local 2 ms RMS — the natural cut point in the quiet dip
   before the hit. Re-trigger catches the full attack; hammer drums
   grade recovered A 0.808 → S 0.988, bass 0.861 → S 0.916.

2. Exports ship DC-free (B2), mirroring vox._finish_clip (4a74213c):
   the demucs stems' ~1e-4 DC bias was flowing into every exported loop
   (all three OLD superfreak kit files flag dc-offset on re-grade
   today). Mean-subtract after mono-sum, before write; shifts the
   zc-snapped edges by ≤1e-4 — inaudible, still effectively zero.

86 tests green.