Pin Python 3.11 + loosen torch; gracefully handle missing plotly

Author: Yuma-Ichikawa

app/_common.py

@@ -10,11 +10,20 @@
 
 import networkx as nx
 import numpy as np
-import plotly.graph_objects as go
 import streamlit as st
 
 import qqa
 
+try:
+    import plotly.graph_objects as go
+except ModuleNotFoundError as exc:  # pragma: no cover - surface a friendlier error
+    st.error(
+        "The `plotly` package is required for the dashboard. "
+        "Add it to `requirements.txt` (or run `pip install plotly`)."
+    )
+    st.stop()
+    raise SystemExit from exc
+
 # Default snippet shown in the Custom-problem editor. It implements a simple
 # Sherrington–Kirkpatrick-style spin glass that the user can adapt freely.
 DEFAULT_CUSTOM_SNIPPET = '''import torch

requirements.txt

@@ -11,19 +11,21 @@
 # only consumed by pip-based deploy targets (Streamlit Community Cloud,
 # Hugging Face Spaces, Render, etc.).
 
+# CPU-only PyTorch wheel (avoids the 900MB CUDA build that would blow
+# through the 1GB Streamlit Community Cloud image budget).
 --extra-index-url https://download.pytorch.org/whl/cpu
-torch==2.4.1+cpu
+torch>=2.2,<2.8
 
-numpy>=1.24
+numpy>=1.24,<3
 networkx>=3.1
 scipy>=1.11
 matplotlib>=3.8
 tqdm>=4.66
 
-# Interactive plots + GUI
+# Interactive plots + GUI (REQUIRED by app/_common.py at import time).
 plotly>=5.17
 pandas>=2.0
 streamlit>=1.30
 
-# Install this repository (reads pyproject.toml)
+# Install this repository so ``import qqa`` works inside the app.
 .

runtime.txt

@@ -0,0 +1 @@
+python-3.11