POSE-10 forensics: RT-RENDER merged horizon pk-pk 234 counts (sky 187) with
the dominant period 165.7 scenes = EXACTLY one camera revolution (21.83 rpm
@ 60 fps -> 164.9); POSE-RT-COMPOSITE real slices the same. Cause: the
per-SCENE zero-DC sky median (Config.dc_level=NaN auto) oscillates with
azimuth as warm terrain sweeps through the sky half; downstream temporal
averages convert the wobble into content-correlated residuals - the faint
rotating ghost ('real image treated as FPN'). Oracle MERGED-DBG shows a
separate, 3-6x smaller wobble at the same period (pre-existing, prepared
path - not addressed here).

Fix (Andrey's rule: one constant per sequence, from the average scene):
- CuasRT.sequenceDcLevel(): manual curt.dc_center override when nonzero,
  else the RT-STATE value derived by appropriateCenter() from the borrowed
  center (= the sequence average) - scenes and center shift by the
  IDENTICAL constant.
- CuasPoseRT (A2 ingest) + CuasRender (render test) now pass a Config with
  that dc_level instead of null; NaN fallback (per-scene) kept but warns
  loudly. Config.dc_level doc updated.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>