Addressing the feedback left on a previous PR of mine:
https://github.com/zed-industries/zed/pull/46663. I feel like this is
worthy of a setting. Note, however, that this does not apply to typing
`ctrl-c` in the terminal from within the agent panel; this is purely
controlling what happens when you click on the "Stop" button in the
terminal tool call card.

Release Notes:

- Agent: Added a setting for controlling the behavior of the stop button
in the terminal tool call card (between cancelling the command to run
and the thread, or just the command).