Runtime fallback: install local detectron2 if import fails (no build isolation)

mvp.py

@@ -51,7 +51,7 @@ REPO_ROOT = os.path.dirname(os.path.abspath(__file__))
 sys.path.append(os.path.join(REPO_ROOT, "vggt"))
 MK_PATH = os.path.join(REPO_ROOT, "MaskClustering")
 DETECTRON2_ROOT = os.path.join(REPO_ROOT, "MaskClustering", "third_party", "detectron2")
-sys.path.append(os.path.join(REPO_ROOT, "MaskClustering", "third_party"))
+sys
 
 # Ensure local detectron2 is installed at runtime if postBuild didn't run
 try:
@@ -638,8 +638,15 @@ def reconstruct(
         subprocess.run(
             [
                 sys.executable,
-                "-m",
-                "detectron2.projects.CropFormer.demo_cropformer.mask_predict",
+                os.path.join(
+                    MK_PATH,
+                    "third_party",
+                    "detectron2",
+                    "projects",
+                    "CropFormer",
+                    "demo_cropformer",
+                    "mask_predict.py",
+                ),
                 "--config-file",
                 os.path.join(
                     MK_PATH,