`ask_user` tool should allow Ctrl-G to support long freeform answers

[pmer]

Describe the feature or problem you'd like to solve

To support multi-paragraph long freeform answers, allow the user to compose a response to the ask_user tool in their $EDITOR

Proposed solution

When describing situations to Copilot CLI, it is often helpful to provide additional context and information.

Currently, if an ask_user is going in the wrong direction, the user can either type in the freeform answer spot, which works poorly if more than few lines, for example, #3722, or the user can Ctrl-C to kill the ask_user tool, then hit Ctrl-C a second time to stop Copilot from continuing, and then finally type Ctrl-G to enter into $EDITOR to compose the desired response to the ask_user.

Additionally, since the user had to leave the ask_user tool with Ctrl-C, if the user later decides they want to respond to the ask_user tool with a non-freeform answer, the option is gone since the tool is no longer running.

The user experience would be improved if Ctrl-G were allowed during an ask_user tool call.

Example prompts or workflows

Here's a screenshot of an example of the issue:

Additional context

No response