Cell magic uses incorrect IPython shell

[krassowski]

Description

When cell magics are spawned in a different shell than global (which may be missing) an incorrect ipython shell is used. This is because instead of using the shell passed to the constructor:

jupyter-ai/packages/jupyter-ai-magics/jupyter_ai_magics/magics.py

Lines 139 to 140 in 512d642

	def __init__(self, shell):
	super().__init__(shell)

get_ipython() gets called:

jupyter-ai/packages/jupyter-ai-magics/jupyter_ai_magics/magics.py

Lines 568 to 570 in 512d642

	# interpolate user namespace into prompt
	ip = get_ipython()
	prompt = prompt.format_map(FormatDict(ip.user_ns))

Reproduce

Run nested shells, or in environment where get_ipython() returns null

Expected behavior

Proper shell is used, get_ipython is never called in library code.

Context

Latest version