fix(build): copy public directory after building same environment with write=false

[artemxknpv]

fixes #22305

prepareOutDirPlugin was marking an environment as rendered even when build.write was false. If the same environment was built again with write set back to true, prepareOutDir() was skipped and publicDir was not copied.

This only marks the environment as rendered when prepareOutDir() actually runs.

Added a regression test for building the same client environment with write: false first and write: true second.

Checks:

• pnpm --filter vite build
• pnpm test-unit build
• pnpm --filter vite typecheck
• pnpm exec eslint --cache --concurrency auto packages/vite/src/node/plugins/prepareOutDir.ts packages/vite/src/node/__tests__/build.spec.ts

[artemxknpv]

@bluwy hi, quick check: is this still worth a look?

CI is green now. happy to adjust if you’d prefer a different approach.

[sapphi-red]

Thanks!