fix: IS 4.5.0 -> 5.0.0 migration — USD metadata, DomeLight, scene reuse

- Fix USD metersPerUnit/upAxis for IS 5.0.0 (no longer auto-compensated)
- Batch fix all Aligned_obj.usd, table, and art USD files with backups
- Fix DomeLight rotation to Z-axis only (prevent tilted environment map)
- Fix scene reuse across episodes (arena_file caching, task clearing, prim guard)
- Add migration tools: scan_usd_metadata.py, fix_usd_metadata.py
- Add migration guide: migerate/migerate.md
- Add nvidia-curobo to .gitignore
- Fix sort_the_rubbish config: obj_0 -> obj_1 (obj_0 does not exist)

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

migerate/scan_usd_metadata.py

@@ -0,0 +1,70 @@
+"""
+Scan all USD files in the project and report their metersPerUnit / upAxis metadata.
+
+Usage:
+    python migerate/scan_usd_metadata.py [--root DIR]
+
+Default root: current working directory (project root).
+"""
+import argparse
+import glob
+import os
+import sys
+
+from pxr import Usd, UsdGeom
+
+
+def scan(root: str, target_mpu: float = 1.0, target_up: str = "Z"):
+    usd_files = glob.glob(os.path.join(root, "**", "*.usd"), recursive=True)
+    usd_files = [f for f in usd_files if not f.endswith(".bak")]
+    usd_files.sort()
+
+    ok_files = []
+    diff_files = []
+    error_files = []
+
+    for fpath in usd_files:
+        try:
+            stage = Usd.Stage.Open(fpath)
+            if stage is None:
+                error_files.append((fpath, "Cannot open stage"))
+                continue
+            mpu = UsdGeom.GetStageMetersPerUnit(stage)
+            up = UsdGeom.GetStageUpAxis(stage)
+            rel = os.path.relpath(fpath, root)
+            if mpu == target_mpu and up == target_up:
+                ok_files.append((rel, mpu, up))
+            else:
+                diff_files.append((rel, mpu, up))
+        except Exception as e:
+            error_files.append((fpath, str(e)))
+
+    # Report
+    print(f"Scanned {len(ok_files) + len(diff_files) + len(error_files)} USD files under: {root}")
+    print(f"  OK (mpu={target_mpu}, up={target_up}): {len(ok_files)}")
+    print(f"  Different: {len(diff_files)}")
+    print(f"  Errors: {len(error_files)}")
+
+    if diff_files:
+        print(f"\n{'='*80}")
+        print(f"Files with non-standard metadata (mpu != {target_mpu} or up != {target_up}):")
+        print(f"{'='*80}")
+        for rel, mpu, up in diff_files:
+            print(f"  mpu={mpu:<8} up={up:<4}  {rel}")
+
+    if error_files:
+        print(f"\n{'='*80}")
+        print("Files with errors:")
+        print(f"{'='*80}")
+        for fpath, err in error_files:
+            print(f"  ERROR: {fpath} -> {err}")
+
+    return diff_files
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Scan USD files for metersPerUnit/upAxis metadata")
+    parser.add_argument("--root", default=os.getcwd(), help="Root directory to scan (default: cwd)")
+    args = parser.parse_args()
+    diff = scan(args.root)
+    sys.exit(1 if diff else 0)