Exiting interact mode in %%debug cell

If I start a debug session with `%%debug` at the start of a cell, and then drop into interactive mode with `interact` I can't find a way to get out of interactive mode. In pdb in the terminal ctrl-D does it, but that just offers to bookmark the page in chrome. Various combinations of `exit/quit/exit()/q/etc` just give NameError - not defined. `import sys; sys.exit()` kills the entire debug process.

Apologies if this is answered somewhere, but a fair amount of searching (e.g. https://stackoverflow.com/questions/45814503/how-to-properly-exit-ipdb-interactive-console-in-jupyter-notebook, https://stackoverflow.com/questions/47522316/exit-pdb-interactive-mode-from-jupyter-notebook) didn't turn up anything.

I'm using jupyter version 4.4.0

Reproduce a cell beginning with %%debug, enter interact, and compare its exit behavior with terminal pdb's Ctrl-D. Trace how the notebook handles the interact session and identify an exit path that does not terminate the debug process. Done means interactive mode can be exited reliably in a Jupyter notebook.

Written by the indexing model from the issue text.