Pixi preview

[hameerabbasi]

Summary

Test plan

• pre-commit run --all-files passes
• Launched the affected UI or script and exercised the change
• Tested with at least one real preset / config when relevant (note which: ____)

AI assistance

• No AI involvement
• AI-assisted — I have read every line in this diff and can defend each change
• Early AI prototype — opened for discussion, not ready for review

[dxqb]

there is too much new code pulled in from current Nerogar:master
I can't review all that. If the UI fix in preview should be fixed before, please do a PR that only changes that against Nerogar:preview
Or just wait for the next preview build
Preview is a testing tool, not intended for wider use. Things can break. I think it only has gotten wider use because @Koratahiu has added an interesting optimizer that people wanted to use. Hopefully we can merge that one soon.

[hameerabbasi]

@dxqb Only the pixi fixes included now.