With rolldown-vite, use lightningcss config from vite config and/or default optimize to false

[wimbarelds]

In Rolldown-vite, the default value for viteConfig.build.cssMinify is 'lightningcss', ie: the same as tailwindcss v4.

As I understand it, there's no reason for both tailwindcss and vite to both minify the CSS using lightningcss; but if there is a good reason for both to do this it would be helpful if tailwindcss could adopt the lightningcss config from viteConfig.css.lightningcss.

Context:
I was having an issue with some bleeding edge CSS (namely custom css @function and @property) logging unknown-at-rule warnings. I configured viteConfig.css.lightningcss.customAtRules, but only half the warnings disappeared. The warnings coming from tailwind's vite plugin "optimize" were still coming through (since tailwindcss does not adopt vite's config for lightningcss). I ended up running the tailwind viteplugin with optimize=false tailwindcss({ optimize: false }) to get rid of all the warnings. I worried this would increase the bundle size, but it did not (it got about 1% smaller), I assume the bundle did not get bigger because the minify from vite's lightningcss was still being applied.