Fix bugs

app.py

@@ -31,7 +31,7 @@ model.eval()
 # ─── INFERENCE + VALIDATION ────────────────────────────────────────────────────
 
 @spaces.GPU  # dynamically allocate & release a ZeroGPU device on each call :contentReference[oaicite:0]{index=0}
-def infer_chatts(prompt: str, csv_file) -> tuple:
+def infer_chatts(prompt: str, csv_file):
     """
     1. Load CSV: first column = timestamp, other columns = TS names.
     2. Drop empty / all-NaN columns; enforce <=15 series.