Update image loader to support subdirectory structure

src/mcr/data/emcr.py

@@ -58,9 +58,7 @@ class SearchTaoTask(RetrievalTask):
 
             if content_id not in corpus:
                 img = row.get("doc_image") or ""
-                img_path = os.path.join(self._image_dir, img) if (self._image_dir and img) else ""
-                if img_path and not os.path.exists(img_path):
-                    img_path = ""
+                img_path = _find_image(self._image_dir, img) if (self._image_dir and img) else ""
                 corpus[content_id] = {"text": _render_doc(row), "image": img_path}
 
             if query_text not in query_index:
@@ -109,6 +107,18 @@ class SearchTaoTask(RetrievalTask):
         }
 
 
+def _find_image(image_dir: str, filename: str) -> str:
+    """Find image in flat dir or part_N subdirectories."""
+    direct = os.path.join(image_dir, filename)
+    if os.path.exists(direct):
+        return direct
+    for subdir in ("part_0", "part_1", "part_2", "part_3"):
+        candidate = os.path.join(image_dir, subdir, filename)
+        if os.path.exists(candidate):
+            return candidate
+    return ""
+
+
 def _task_group(task_type: str) -> str:
     """Coarse group: price+negative > price > negative > general."""
     has_price = "price" in task_type