CLAUDE: fopen_pose_compare.py — add orientation comparison + cumulative rotation

- parse_images_txt: store full R_cw (world→camera rotation) per frame
- new compute_orientation_data(): per-frame COLMAP and ERS orientation
  in Sim(3)-aligned GPS frame; delta-rotation angle (convention-independent);
  cumulative rotation integrated from frame 0
- new print_orientation_report(): per-frame RMSE + cumulative totals
- ers_to_R(): guessed convention Rz(az)*Rx(tilt)*Ry(roll) — to be verified
- CSV: adds colmap_yaw/pitch/roll, delta_colmap/ers/diff, cum_colmap/ers/diff

Key finding for water-tower straight-flight (378 frames):
  COLMAP cumulative rotation = 120.81° (photogrammetric noise ~0.25°/frame)
  ERS cumulative rotation    =  14.10° (physically correct: 1.9° heading + vibration)
→ COLMAP orientation is dominated by pose-estimation noise for pure-nadir SfM
→ orientation comparison meaningful only for LARGE angular changes (turning sequences)
→ position comparison (Sim(3) RMSE) remains the primary validation metric
Co-authored-by: Claude <claude@elphel.com>