Add 16 new tests targeting previously uncovered code paths in
rotation_averaging.cc:
- skip_initialization option (zero-init solver path)
- HALF_NORM weight type in IRLS
- Deterministic random seed (reproducibility)
- Disabled rotation error filtering (max_rotation_error_deg <= 0)
- Empty pose graph error handling (known and unknown rig paths)
- Gravity with unknown rig sensors (AllSensorsFromRigKnown failure)
- filter_unregistered option (refinement pass)
- Stratified gravity skipped when >95% pairs have gravity
- Gravity without stratified solving
- Gravity enabled but no priors present (UseGravity false path)
- InitializeRigRotationsFromImages (multi-camera and empty input)
- Tight rotation error filtering with frame deregistration
- Edge invalidation by relative rotation error
- Unknown rig with noise (expanded reconstruction path)

Increase num_frames_per_rig from 5 to 15 to make the IRLS system
better conditioned with HALF_NORM weights, fixing CHOLMOD
non-positive-definite failures on macOS. Also fix clang-format issues.

ahojnnes marked this pull request as ready for review