Improve sub-shell experience in terminal inline chat

[anthonykim1]

The current experience of using inline chat in sub-shell is not ideal, in a way that it does not realize that user is in a sub-shell. This is even though the shell type has changed.

For example, if I were to enter Python sub-shell from zsh, and then request inline chat to print hello world in Python, it would give me a suggestion or command of python3 -c "print('hello world')", which is not good.

This is not good because we are already in a Python REPL or Python sub-shell, and python3 -c is completely unnecessary.

We should give context for inline chat about shell type, or figure out if its missing context for sub-shell scenarios. Or figure out what else is causing this issue.

[anthonykim1]

Verification steps:

1. Enter into subshell such as typing python or node in your terminal
2. trigger inline chat and try to generate some command specific to your subshell.
3. Make sure copilot generated appropriate command for your subshell. (For example asking to print hello should NOT generate python3 -c... etc but rather print('hello')