A feature to set a default kernel other than python for Jupyter Notebook

[matthewgson]

Following the discussion and suggestions from #6244, it would be great to add a feature to set a default kernel other than Python, especially for a workspaceless environment in Positron.
Additionally, having an option to override the workspace’s default (Python) kernel would be beneficial.

[testlabauto]

Checked with @sharon-wang and this is not currently work she was planning (although there is some overlap).

Tagging @seeM as he may know if we are already planning this work for the notebook experience.

Moving to Triage for prioritization.

[juliasilge]

Let me ask here again like I just did in #6244:

Do you want to set a default interpreter only for notebooks, or would it work for you to set a default interpreter for all consoles and notebooks? In #6145 we added the ability to set language level startup settings. If you set R to "auto" and Python to "manual" then all new interpreters that Positron starts (console or notebook) will always be R, unless you specifically go and start Python yourself (such as from the command palette with "Python: Select Interpreter".

Would that work for you @matthewgson? Or are you only wanting this behavior for notebooks?

[matthewgson]

For me, I think it would be great to set a default interpreter only for notebooks. I treat .ipynb notebooks as a distinct realm in my workflow—especially when using the Positron IDE—and I’d love for the kernels they use to remain isolated so they don’t interfere with any ongoing Python or R sessions. I’m not sure how other users mentally approach .ipynb files, but I’d be happy if you could consider this perspective.