Allow client to edit tool calls during permission requests

[WhiskeyJack96]

Use case:
User are presented with a request to "approve" an Edit to a file. This can be presented as a diff to a file and the user can make their choice.
If an edit is "close" and the user would like to tweak it slightly before approving there doesnt appear to be a way to do this within the protocol.

As far as I can see one possible alternative would be to change fs/write-text-file to re-compute the diff and open it to allow the user to edit it but that feels a bit lame (in that the user had to approve it then re-interact. Maybe this is mitigated by defaulting to "approve" on edit/writes and delaying the permission but this messes with agents "internal" file state (they won't passively observe the edits).

If this was moved to a Permission handle it could also be extended to bash commands (which would be nice too!) and/or other tool calls.

I'm not sure what agents would support this today, but I know that the ones with native editor integrations should have some mechanism for it. Happy to do more research/contribute/etc if theres interest in this and its feasible!