Vite 8 and Vitest 4

[bienzaaron]

Summary

• Upgrade Vite peer/dev support to Vite 8 and Vitest coverage tooling to Vitest 4.
• Replace Vite 7 raw asset AST loading with Vite 8-compatible raw module code parsing.
• Fix async rejection assertions and normalize build output snapshots under Rolldown-backed Vite builds.

Verification

• pnpm pipeline