Allow for >6 Subagents: Make MAX_THREADS Configurable in CONFIG

What variant of Codex are you using?

Codex CLI

What feature would you like to see?

I would like to see MAX_THREADS be a variable in the CONFIG file so we can run more than 6 subagents at one time.

I have a forked Codex which I'm using to launch more than 6 subagents at a time. It works amazing. I think having 6 default is reasonable, but some of us want more. Please make MAX_THREADS a variable that you can set inside the CONFIG.TOML

My fork allowed for custom subagents, but @jif-oai is a legend and added that for us, so the only thing left I need is more agents.

<img width="342" height="137" alt="Image" src="https://github.com/user-attachments/assets/2af914f7-1e1d-4ea7-a1a6-3a55794cb1c5" />

I built an app in 7 minutes with Spark using 12 parallel agents. This will unlock blistering speed for power users. Please make it so <3

https://x.com/LLMJunky/status/2022712980090105883?s=20

Thank you so much Codex team.

Additional information

_No response_