fix: fix vi.importActual() for virtual modules

[hi-ogawa]

Description

• Closes vi.importActual() issue with virtual modules in Vitest 4 #9771

This PR changes importActual to use ?_vitest_original to fetch original module code. There is already a similar technique on browser mode. Additionally for this to actually work for virtual module, it's necessary to strip ?_vitest_original before it gets into load hook of virtual module. For webdriverio though, this is actually not possible because it relies on plugin pipeline load(originalId) to implement mocking. For others, this is possible since "original id" handling happens outside of vite plugin pipeline.

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[hi-ogawa]

The issue was that previously rawId = "virtual:module" would get short-circuit here for both initial mocked import "virtual:module" and following importOriginal calls, which means the real code never got read by module runner.

This PR adds ?_vitest_original query to importOriginal's fetchModule so that it can return the real module code.

[hi-ogawa]

This is needed to avoid this silly localhost vs 127.0.0.1 errors https://github.com/vitest-dev/vitest/actions/runs/22614377230/job/65523514606#step:8:911

   FAIL  test/browser-multiple.test.ts:7:1 > automatically assigns the port
  AssertionError: expected [ 'http://127.0.0.1:63315/', 'http://127.0.0.1:63316/' ] to include 'http://localhost:63315/'
   ❯ test/browser-multiple.test.ts:31:16
       29|   expect(spy).not.toHaveBeenCalled()
       30|   expect(stderr).not.toContain('is in use, trying another one...')
       31|   expect(urls).toContain('http://localhost:63315/')
         |                ^
       32|   expect(urls).toContain('http://localhost:63316/')
       33| })

[hi-ogawa]

Ideally this should live in playwright provider, but don't think that's possible now, so here it is.

[hi-ogawa]

Actually instead of middleware level rewriting, it should be also possible to just strip ?_vitest_original from resolveId like

resolveId(source) {
  if (source.endsWith("?_vitest_original")) { 
    return source.slice(...)
  }
}

This is because the source comes here is already the resolved id + ?_vitest_original such e.g. "\0virtual:module?_vitest_original".

In fact, I used a similar idea in RSC plugin to "redirect" already resolved id back as something importable https://github.com/vitejs/vite-plugin-react/blob/main/packages/plugin-rsc/src/plugins/resolved-id-proxy.ts.