Description

Resolves #9191

Problems

state.metaEnv = import.meta.env in browser tester.ts is transformed to { "MODE": "production", ...} due to vite build during @vitest/browser packaging. Later we mutate and override metaEnv with config.env, but this logic doesn't accommodate import.meta.env define and doesn't match with Vite dev behavior on browser mode. (On SSR, both import.meta.env define get merged to process.env, so defines works on runtime).

Solutions

I'm not sure this is the only way, but I replaced with a marker __vitest_browser_import_meta_env_init__ to ensure import.meta.env is processed by Vite (which happens during client import analysis).

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