Fix: Update dataset download path for compatibility with HF_HOME environment variable

app.py

@@ -65,8 +65,10 @@ _model_cache: dict = {}
 def get_lance_dataset():
     """Download dataset from HF Hub (cached) and return Lance connection."""
     if "ds" not in _lance_cache:
-        # Use local_dir to get actual files, not symlinks (Lance needs real files)
-        local_dir = "./data/arxiv-lance"
+        import os
+        # Use HF_HOME or /tmp for Spaces compatibility (./data not writable on Spaces)
+        cache_base = os.environ.get("HF_HOME", "/tmp/hf_cache")
+        local_dir = f"{cache_base}/arxiv-lance"
         print(f"Downloading dataset from {DATASET_REPO} to {local_dir}...")
         snapshot_download(
             DATASET_REPO,