perf: cache generated SSR remote entry source

[tonoizer]

Summary

• Cache the generated SSR remote-entry source within each plugin instance.
• Reuse the stable base source across multiple Rollup outputs.
• Preserve independent Nuxt expose-chunk rewriting for every output.
• Add multi-output coverage proving one generation and two correctly rewritten assets.

Motivation

Rollup can invoke output-generation hooks for multiple outputs. The generated SSR entry depends only on normalized federation options, so regenerating the same base source for every output is unnecessary.

Scope

This is intentionally limited to the SSR source-generation path. It does not change environment gating, publication, dev-server behavior, or generated output semantics.

Validation

• git diff --check
• Added focused multi-output Nuxt unit coverage.
• Vitest, typecheck, and formatting could not run in this checkout because node_modules is unavailable.

This is a small optimization; the benefit is proportional to the number of Rollup outputs and may be most useful for multi-output builds.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@module-federation/vite@1040

commit: ab4de6a

[gioboa]

Thanks @tonoizer
Nice one 👏