feat: implement ICP registration for ground plane refinement and add tests

py_workspace/.sisyphus/notepads/icp-registration/decisions.md

@@ -0,0 +1,4 @@
+## Notes
+- Used `scipy.spatial.transform.Rotation` with `xyz` Euler convention for gravity regularization to ensure consistent blending of pitch/roll.
+- `extract_near_floor_band` uses dot product with floor normal to handle arbitrary floor orientations (not just Y-up).
+- `refine_with_icp` uses a BFS-based connectivity check to ensure only cameras reachable from the reference camera are optimized.

py_workspace/.sisyphus/notepads/icp-registration/learnings.md

@@ -14,3 +14,9 @@
 - When monkeypatching for tests, ensure all internal calls are accounted for, especially when production code has bugs that need to be worked around or highlighted.
 - Integrated ICP refinement into `refine_ground_plane.py` CLI, enabling optional global registration after ground plane alignment.
 - Added `_meta.icp_refined` block to output JSON to track ICP configuration and success metrics.
+## ICP Registration
+- GICP method in  requires normals, which are estimated internally if not provided.
+- Synthetic tests for ICP should use deterministic seeds for point cloud generation to ensure stability.
+## ICP Registration
+- GICP method in `pairwise_icp` requires normals, which are estimated internally if not provided.
+- Synthetic tests for ICP should use deterministic seeds for point cloud generation to ensure stability.

py_workspace/.sisyphus/notepads/icp-registration/problems.md

@@ -0,0 +1 @@
+## Notes