Add the TGeo to CAD exporter

This adds O2_TGeoToCAD.py, which writes a TGeo geometry out as a STEP file.

- O2_TGeoToCAD.py walks the TGeoVolume DAG and writes one STEP file that keeps the XCAF assembly
  tree.
- A logical volume becomes one definition, referenced from every node that places it.
- --carve-mothers subtracts the placed daughters from a mother solid for a CAD-facing export.
- --media-json records the source media, so converting the STEP back rebuilds them verbatim.
- The wrapper o2-tgeo-to-cad is installed into bin and runs the script from
  $O2_ROOT/share/CADSupport/tools.
- --self-test covers the mapping.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: sawenzel

Detectors/CADSupport/CMakeLists.txt

@@ -73,3 +73,12 @@ o2_add_executable(
   IS_BENCHMARK
   PUBLIC_LINK_LIBRARIES O2::CADSupport ROOT::Geom ROOT::GeomPainter ROOT::RIO
                         nlohmann_json::nlohmann_json)
+
+install(PROGRAMS tools/o2-tgeo-to-cad
+        DESTINATION ${CMAKE_INSTALL_BINDIR})
+
+install(DIRECTORY tools/
+        DESTINATION ${CMAKE_INSTALL_DATADIR}/CADSupport/tools
+        USE_SOURCE_PERMISSIONS
+        PATTERN "__pycache__" EXCLUDE
+        PATTERN "o2-tgeo-to-cad" EXCLUDE)