Add end-to-end RGB-D reconstruction support across the C++ core and Python API.
- add a native merge_rgbd_views path, view-aware 3D pose containers, and nanobind bindings
- expose Python helpers to sample aligned depth, apply per-joint offsets, lift UVD poses to world space, and run reconstruct_rgbd
- add RGB-D regression tests for merging, manual pipeline parity, symmetric depth sampling windows, and out-of-bounds joints
- bump the project version from 0.1.0 to 0.2.0 for the new feature surface
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