Add /fix slash command

[dlqqq]

This PR introduces a new /fix slash command that fixes a code cell with error output when selected in an open notebook.

• /fix only works when a code cell with error output is the active cell. Otherwise the UI prevents /fix from being sent.
• /fix also accepts additional instructions in natural language following /fix.
  For example: /fix Fix this code cell by using the numpy library only.
• The code action toolbar can used to quickly replace the active cell with the revised code suggested by Jupyternaut.

Demo video

Screen.Recording.2024-06-11.at.10.49.17.AM.mov

[srdas]

Thanks for adding this, it is very useful, and should really help developers a lot.

[1] Tested the branch and it works well and nothing else seems to be broken.

[2] Tested that the /fix command works in an active cell that has an error whether you click on the code or the output.

[3] Tested that when the cell does not have an error, then /fix cannot be used.

[4] Tested that when the cell has only a warning, then /fix cannot be used. Do we want to have /fix work for cells with warnings?

[5] Nit: "Insert below active cell" (see below) does not say if the code will be inserted in the cell below (overwriting it) or insert a new cell and add the new code to it. The action is the latter but may be we want to point it out. (This is not directly related to this PR.)

[6] I am getting a new chat user as shown below, is this intended?

[dlqqq]

@srdas Thank you for the quick review! I've addressed your review feedback in the threads above.

[6] I am getting a new chat user as shown below, is this intended?

This is likely because you have jupyter-collaboration installed in your environment. When this is the case, Jupyter AI automatically infers your identity from the RTC identity provider. When RTC is enabled, the name shown in the chat panel matches the name shown in the collaborators panel.

[srdas]

Awesome work!! Verified all suggestions are implemented! TY!