SolidStart

Solid 2.0 RC introduces a fundamentally async-first reactive system where async operations are integrated directly into the graph. This release also brings a new Rust-based compiler via `@solidjs/vite-plugin` and replaces SolidStart with an integrated 'start mode'.

This maintenance release focuses on bug fixes for CSS parsing, Vite integration (specifically for SolidStart), and refining the behavior of @theme and @variant directives.