Release BIT 4.6.1.\n\nHighlights:\n- Adds nested BOX_FEATURE geometry support for practical parent-tray and child-well layouts.\n- Adds BOX_GROUP transform containers for moving and rotating related features together without creating parent geometry.\n- Updates shipped starter/example includes to boardgame_insert_toolkit_lib.4.6.1.scad.\n\nVerification:\n- ./tests/run_tests.sh --csg-only: 82 passed, 0 failed.\n- ./scripts/package-release.sh --minor smoke-compiled shipped starter/example files.