Support “Add to Codex Thread” for selected code in Jupyter Notebook cells

What variant of Codex are you using?

IDE Extension

What feature would you like to see?

I would like the Codex VS Code extension to support adding selected code
from Jupyter Notebook (.ipynb) cells directly to the current Codex thread.

Environment:

• macOS
• VS Code
• Codex extension version: 26.810.41047
• Microsoft Python and Jupyter extensions installed

Steps to reproduce:

1. Open an .ipynb file in VS Code.
2. Select code inside a Jupyter code cell.
3. Right-click and choose “Add to Codex Thread”.
4. Nothing is added to the Codex composer, and no error is displayed.

Expected behavior:
The selected code should appear as context in the current Codex composer,
including the notebook filename and preferably the cell identity.

Actual behavior:
The command has no visible effect.

Important comparison:
The same selected Jupyter cell code can be added successfully to VS Code’s
built-in Chat, so the notebook selection itself is working.

This feature is important for learning, data analysis, and notebook-based
Python workflows. Copying and pasting manually loses file and cell context.

Additional information

No response

Reproduce the issue in VS Code with an .ipynb file, selected cell code, and the “Add to Codex Thread” command, then trace that command's handling of notebook selections. Compare the working built-in Chat behavior and verify that the selected code reaches the Codex composer with the notebook filename and cell identity.