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>

nimbus_extension/components/load/env_loader.py

@@ -60,7 +60,10 @@ class EnvLoader(SceneLoader):
         if isinstance(rendering_dt, str):
             rendering_dt = float(Fraction(rendering_dt))
 
-        from isaacsim import SimulationApp
+        try:
+            from isaacsim import SimulationApp  # IS 5.x
+        except ImportError:
+            from omni.isaac.kit import SimulationApp  # IS 4.x
 
         self.simulation_app = SimulationApp(
             {