fix: ensure vendored detectron2 on PYTHONPATH for subprocesses

mvp.py

@@ -49,6 +49,11 @@ except Exception:
 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")
+
+# If detectron2 isn't installed as a package, allow importing from vendored source.
+if os.path.isdir(DETECTRON2_ROOT) and DETECTRON2_ROOT not in sys.path:
+    sys.path.append(DETECTRON2_ROOT)
 
 # Writable workdir (HF Spaces: prefer /tmp)
 WORK_DIR = os.environ.get("ZOO3D_WORKDIR", os.path.join(tempfile.gettempdir(), "zoo3d"))
@@ -655,6 +660,14 @@ def reconstruct(
                 os.path.join(MK_PATH, cropformer_name),
             ],
             check=True,
+            env={
+                **os.environ,
+                # Ensure detectron2 is importable even if not installed via pip
+                "PYTHONPATH": DETECTRON2_ROOT
+                + os.pathsep
+                + MK_PATH
+                + (os.pathsep + os.environ["PYTHONPATH"] if os.environ.get("PYTHONPATH") else ""),
+            },
         )
 
         subprocess.run(
@@ -672,7 +685,12 @@ def reconstruct(
         )
 
         env = dict(os.environ)
-        env["PYTHONPATH"] = MK_PATH + (os.pathsep + env["PYTHONPATH"] if env.get("PYTHONPATH") else "")
+        env["PYTHONPATH"] = (
+            DETECTRON2_ROOT
+            + os.pathsep
+            + MK_PATH
+            + (os.pathsep + env["PYTHONPATH"] if env.get("PYTHONPATH") else "")
+        )
         subprocess.run(
             [
                 sys.executable,
@@ -941,7 +959,12 @@ def detect_objects(text_labels, target_dir, conf_thres, *viz_args):
             print(f"Text features: {text_features}")
             try:
                 env = dict(os.environ)
-                env["PYTHONPATH"] = MK_PATH + (os.pathsep + env["PYTHONPATH"] if env.get("PYTHONPATH") else "")
+                env["PYTHONPATH"] = (
+                    DETECTRON2_ROOT
+                    + os.pathsep
+                    + MK_PATH
+                    + (os.pathsep + env["PYTHONPATH"] if env.get("PYTHONPATH") else "")
+                )
                 root_input_dir = os.path.dirname(target_dir)
                 seq_name = os.path.basename(target_dir)
                 subprocess.run(