Adding code cell after non-runnable code cell creates a runnable cell

[gjsjohnmurray]

Issue Type: Bug

1. Create a notebook extension in which code cells are set runnable or not runnable when a notebook is opened, based on the language mode of the stored cells.
2. Click the +Code button after a non-runnable cell.
3. Observe that the new cell has the same language mode 👍 but it is runnable 👎

VS Code version: Code - Insiders 1.53.0-insider (8490d3d, 2021-02-03T15:53:41.416Z)
OS version: Windows_NT x64 10.0.19042

[vscodebot]

(Experimental duplicate detection)
Thanks for submitting this issue. Please also check if it is already covered by an existing one, like:

• Native Notebooks - Add code cell not working after markdown (#115432)
• Native Notebooks - Add Code Cell (#108464)
• Run info in notebook metadata (#106747)
• Add command to insert copied cells above the current cell (#114720)
• Allow extensions to call cell commands with cell arguments (#98282)

[gjsjohnmurray]

In contrast, metadata.breakpointMargin does get carried forward to the new code cell 👍

[gjsjohnmurray]

Contrast this with what copy+paste does with metadata

#103881 (comment)

[roblourens]

I think this would have been based on the cellRunnable property and require the extension to jump in and fix up runnable, but all of this has been deleted and the runnability is now inferred based on kernel+language, so it should be good now.