rsc: strip server route exports from optimizeDeps scan

[KimHyeongRae0]

Fixes #14934.

Adds a scanner-only Rolldown transform so RSC route entries drop server exports before Vite 8's client optimizeDeps scan follows imports.

Validation:

• pnpm test -- packages/react-router-dev/__tests__/rsc-virtual-route-modules-test.ts --runInBand
• pnpm --filter @react-router/dev typecheck
• pnpm playwright:integration --project=chromium integration/vite-dev-test.ts -g "does not prebundle RSC server-only route imports"
• pnpm exec prettier --check packages/react-router-dev/vite/rsc/plugin.ts packages/react-router-dev/vite/rsc/virtual-route-modules.ts packages/react-router-dev/vite/vite.ts packages/react-router-dev/__tests__/rsc-virtual-route-modules-test.ts integration/vite-dev-test.ts packages/react-router-dev/.changes/unstable.rsc-optimize-deps-route-scan.md

[remix-cla-bot]

Hi @KimHyeongRae0,

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- The Remix team

[remix-cla-bot]

Thank you for signing the Contributor License Agreement. Let's get this merged! 🥳