Replaces the absolute curt_pose_max_dxy with the scale-free scheme (Andrey's
histogram rule formalized + robustness for worse footage):
- Calibration artifact -POSE-RT-MAXDXY.tiff: per-tile max-over-scenes residual,
  +inf where any scene NaN (auto-reject, mergeable across runs by max), NaN
  where unmeasured. Saved only from FULL-selection runs (a filtered run never
  shrinks coverage). Continuous statistic persisted, boolean selection derived
  at load - policy can change without re-measuring.
- deriveSelection(): stage 1 outlier gate keep max <= median + k*NMAD of finite
  per-tile maxes (curt_pose_dxy_k=0.75; on the reference footage: MBEN gate
  0.477 keeps 595, degraded NOMB self-adapts to 0.728 keeps 626 - same ~65%);
  stage 2 rank-N budget keep curt_pose_num_tiles=150 best (threshold-free).
- curt_pose_use_filt now loads MAXDXY and derives; missing -> full run
  generates it (FPN-style reuse pattern).
Importance-greedy (3x3 information matrix) ranking = next step.

mvn compile clean.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>