Make it easier to interrupt the agent with a new message

[leo-ease]

Currently we can queue up the next message, but as far as I can tell there is no straightforward way to interrupt/course correct the model as it's working and send a new message immediately. To do this, you have to hit "Terminate" first, which also then discards your queued message.

Suggested UX:
-Type message and hit enter/send once to queue (same as current)
-Hit enter a second time immediately to interrupt and send now (new flow. Windsurf works in a similar way.)
Could also be a button shown next to the queued message.