fix: IS 4.1.0 + Blackwell GPU compatibility fixes

- Add scipy Rotation scalar_first monkey-patch for older scipy (<1.11)
- Fix SimulationApp import to support both IS 4.x and 5.x
- Reuse task object across reset() calls to prevent duplicate prims
- Add _scene_initialized guard in set_up_scene() for repeated resets
- Cache arena_file_path to survive task_cfg.pop()
- Clean up collision groups before re-creating
- Switch to PathTracing renderer for clean output on Blackwell GPU

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

workflows/simbox/core/utils/collision_utils.py

@@ -27,6 +27,11 @@ def filter_collisions(
     # We invert the collision group filters for more efficient collision filtering across environments
     physx_scene.CreateInvertCollisionGroupFilterAttr().Set(True)
 
+    # Clean up existing collision groups before re-creating (handles repeated reset() calls)
+    collision_prim = stage.GetPrimAtPath(collision_root_path)
+    if collision_prim.IsValid():
+        stage.RemovePrim(collision_root_path)
+
     UsdGeom.Scope.Define(stage, collision_root_path)
 
     with Sdf.ChangeBlock():