[Feature]: Add a Codex-style /side command

[Lermatroid]

It would be great to have something like Codex’s /side for quick ephemeral side thread from the current conversation to explore a question without derailing the main thread in the side panel.

Example of what this looks like: https://x.com/Dimillian/status/2049929842133520577

[lastobelus]

This is particularly useful when your side query

a) needs the main thread context and
b) will have verbose output, and therefore trigger a compaction (or add significant token cost to subsequent turns) if you ask it in the main thread

[joshua-redmond-1st]

Yes! I really miss the side chat/btw feature when I use T3 Code

I love T3 Code, but the rest of my team doesn't want to use it because it's not got this feature lol