Open3D SLAC Adapter

Calibrex treats Open3D SLAC as an optional backend, not a core dependency.

Run the adapter example:

calibrex calibrate examples/rgbd_open3d_slac/config.yaml

The example dataset manifest declares RGB-D fragments and pose graph metadata. When open3d is not installed, Calibrex reports open3d_slac_status: not_executed in result provenance and emits WARN quality diagnostics. This keeps result.yaml, report.html, and evaluation behavior stable across machines with and without Open3D.