Design 3-A4i rung A (2026-07-16 handoff): the 00:25:48 gate profile's
'leanMeasure other' (26.1 ms/call, 43% of post) was unprofiled debug-save
data motion (pose_corr_save/pose_img_save). Changes:
- leanFitScene passes corr_pd_out/img_out only on the LAST outer cycle in
  fixed-cycle mode (legacy convergence mode keeps every-cycle so an early
  exit still fills the holders).
- New DEBUG_FETCH profile stage wraps perSensorImagesFromTD, the no-MB
  debug re-convert, and fetchNormalizedPD, so debug data motion can never
  hide in 'leanMeasure other' again (it joins measureAccounted).
Armed pose_corr capture unaffected (fetch keyed on isArmed() unchanged).
Expected gate: poses/records byte-exact, hyperstacks identical, capacity
~3.9 -> ~5.5 scenes/s in the debug config.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>