Enable --threads for all tasks, or have more efficient CPU usage across tasks

[Michael-M-Judd]

In the advent of agentic workflows, we can have many processes all running biome lint or biome format.

Ideally, biome should be smarter about not using 100% CPU at all times for massive codebases if there are a number of other biome instances running.

Common workflow:

• Agents run biome lint after finishing their task
• Have 6 agents running at once
• Each biome quickly uses 60-80% CPU (at least in my large codebase)

Issue: Resource contention, slow linting across multiple processes

A simple solution to this IMO is that we should just allow --threads to exist for all calls, not just ci that currently enables it. This way, users can limit biome threads to 1 to ensure threads are healthy across parallel agents.

[dyc3]

Currently, we use rayon for actually doing the multithreading, so as a workaround you can set the RAYON_NUM_THREADS environment variable to limit the spawned threads. This will probably work better for your agents because you can just set the environment variable, and you don't have to instruct them to use it!

[Michael-M-Judd]

That makes sense. Happy to update the docs on this so that its clear. I didn't immediately find this when doing a quick search through the repo.

[ematipico]

PRs welcome