…dustries#50490)

This PR changes the behavior of editing queued messages. Previously, you
could type directly in the editor that was used to displayed a queued
message. However, that felt a bit anxiety-inducing because there was a
chance the message would get sent before you could've wrapped up your
edits. And even if we blocked the message to get sent while focused on
the editor, it could still be a bit unpredictable. So, with this PR, if
you type on a queued message, the content of that message goes
immediately back to the main message editor. Effectively, you're taking
that message off the queue so you can edit it, and then if you hit enter
(while there's a generation ongoing), that content goes back into the
queue.

I believe this allows for a calmer editing experience when wanting to
touch up or increment a queued message.

Here's a video of the flow:


https://github.com/user-attachments/assets/ec60ccad-2b04-4b7c-a8f5-95baa443d9f2

In the video, I'm showcasing a few things:
- in case the main message editor already had content, the content from
the edited queued message is appended to it. That avoids the user
surprisingly losing information.
- the fact that mention creases still work well and are not converted
back into plain text

Release Notes:

- Agent: Made editing queued messages better by moving the contnet back
to the main message editor, avoiding the chance of it getting sent
mid-editing.