chore: upgrade Rolldown 1.0.0-rc.18, Vitest 5.0.0-beta.1 (#414)

Automated daily upgrade of Vite, Rolldown, and/or Vitest to the latest available versions.

Rolldown: 1.0.0-rc.17 → 1.0.0-rc.18 Vitest: 4.1.5 → 5.0.0-beta.1

Updated locations

• packages/react-server/package.json — vite, rolldown
• test/package.json — vite, rolldown, vitest, @vitest/ui
• packages/rsc/package.json — vitest, @vitest/*
• packages/create-react-server/test/package.json — vitest
• package.json — all pnpm.overrides for Vite
• pnpm-lock.yaml

Smoke test

• Dev mode — hello world test passed ✅
• Build+start mode — hello world test passed ✅

Co-authored-by: lazarv 1749493+lazarv@users.noreply.github.com