fix(dev): ignore external Vite server environments

[raashish1601]

Closes #14937.

Summary

• only treat ssr / ssrBundle_* as React Router-owned server environments
• skip the server-build manifest cleanup path for unrelated environments added by other Vite plugins
• add focused Jest coverage for the server-environment filtering logic

Validation

• corepack pnpm test packages/react-router-dev/__tests__/vite-plugin-test.ts
• corepack pnpm --filter @react-router/dev build

[remix-cla-bot]

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- The Remix team

[p-dubovitsky]

A duplicate of #14883

[remix-cla-bot]

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

[raashish1601]

Compared this against #14883 in detail. There is overlap in packages/react-router-dev/vite/plugin.ts, but the two PRs are not identical today: #14883 only gates the writeBundle / prerender SSR-only paths, while this branch also threads the React Router server-environment filter through configEnvironment() and the shared getServerEnvironmentEntries() / getServerEnvironmentKeys() helper used by the environment-config path, with direct unit coverage in packages/react-router-dev/__tests__/vite-plugin-test.ts.

If you'd prefer to keep a single branch, I'm happy to fold the configEnvironment / helper coverage into #14883 instead. I also pushed 012c9c0 to add raashish1601 to contributors.yml so the CLA bot can re-check this branch.

[github-actions]

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