PR Checklist

On Vite 8 (rolldown), the dep optimizer compiler plugin runs Angular's JavaScriptTransformer over every prebundled .js/.cjs/.mjs dependency even in test mode, and never closes the transformer's worker. The esbuild variant of the same plugin skips the transform in test mode (if (!isTest)) and closes the transformer in onEnd. Large packages in optimizeDeps.include can stall the optimizer before the vitest RUN banner because everything funnels through that single never-closed worker.

Closes #2371

Affected scope

• Primary scope: vite-plugin-angular
• Secondary scopes: none

Recommended merge strategy for maintainer [optional]

• Squash merge
• Rebase merge
• Other

Commit preservation note [optional]

n/a

What is the new behavior?

createRolldownCompilerPlugin now takes the same isTest and closeTransformer flags as the esbuild variant:

• in test mode it does not register the load transform, so prebundled deps are not piped through the Babel linker — same as the esbuild path;
• when closeTransformer is set (everything except the Astro integration), the transformer is closed in buildEnd. JavaScriptTransformer.close() resets its lazy worker pool, so a later optimizer run re-creates it on demand.

createDepOptimizerConfig passes opts.isTest and !opts.isAstroIntegration, mirroring the esbuild call right below it.

Test plan

• nx format:check
• pnpm build (nx build-package vite-plugin-angular, tsc, no errors)
• pnpm test (full workspace green; nx test vite-plugin-angular: 625 passed, 3 skipped)
• Manual verification: new unit tests in compiler-plugin.spec.ts fail on the old code (the load hook was registered in test mode; no buildEnd) and pass with the fix

Does this PR introduce a breaking change?

• Yes
• No

createRolldownCompilerPlugin is internal — the package entry point only exports angular. The only call site is createDepOptimizerConfig.

Other information

The rest of the dep optimizer behavior on the rolldown path is unchanged.