Fix notebook CI: increase timeout, exclude slow TROP notebook

- Increase per-notebook timeout from 300s to 600s (pure Python mode
  without Rust backend is significantly slower for Monte Carlo and
  optimization-heavy notebooks)
- Exclude 10_trop.ipynb (LOOCV grid search exceeds 600s in pure
  Python mode)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: igerber

.github/workflows/notebooks.yml

@@ -45,9 +45,12 @@ jobs:
           DIFF_DIFF_BACKEND: python
         run: |
           pytest --nbmake docs/tutorials/ \
-            --nbmake-timeout=300 \
+            --nbmake-timeout=600 \
+            --ignore=docs/tutorials/10_trop.ipynb \
             -v \
             --tb=short
+          # Excluded notebooks:
+          #   10_trop — LOOCV grid search too slow for pure-Python CI (>600s)
 
       - name: Upload failed notebook outputs
         if: failure()