[FEATURE]: allowing commands mid-msg

[oribarilan]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Currently at mentionds (@) are allowed mid msg, but for some reason commands (/) are not.
One annoying example is if a user wants to access /help or change a model after a message was already typed.

Solution: Allow commands at any point of the msg, and don't clear the text input after command was executed.

[oribarilan]

showing suggested implementation in #3580 , in case you want to support this :)