Last pre-release checks and cleanup

I’m finally ready to release v0.1.0-alpha.2. Only notable thing I changed here is that I changed the default thread count: It now defaults to hardware concurrency everywhere. Other than that, I of course did final documentation checks and fixes and now I’m just waiting for CI to pass so I can tag it and let the release workflow do the last step. So this is hopefully the last devlog before my ship!