ci : add ipywidgets 7.7.1 to Colab requirements

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: beachdweller

tests/requirements.colab.2025.02.txt

@@ -10,6 +10,7 @@
 Cython==3.0.11
 graphviz==0.20.3
 html5lib==1.1
+ipywidgets==7.7.1
 jupyter-client==6.1.12
 jupyter-console==6.1.0
 jupyter-server==1.24.0