fix(preview): user vite.preview.allowedHosts in static preview

[spider-yamet]

Changes

• Fixes astro preview static server to merge user Vite config from astro.config.mjs (config.vite) before starting Vite preview.

• Keeps preview defaults/overrides on top (configFile: false, Astro-managed preview fields, Astro preview plugin).

• Applies allowedHosts after merge to avoid Vite array-concatenation behavior.

• Preserves precedence:

  • explicit Astro server.allowedHosts (true or non-empty array) wins
  • otherwise merged vite.preview.allowedHosts is used

• Fixes #16088.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 4332600

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[codspeed-hq]

Merging this PR will not alter performance

✅ 18 untouched benchmarks

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_{Comparing spider-yamet:fix/astro-preview-ignores (4332600) with main (999c875)¹}

Footnotes

1. No successful run was found on main (f649ae0) during the generation of this report, so 999c875 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[spider-yamet]

@delucis seems current ci is failure is no assertion failures just due to timeout, I checked it from the log.
hope you can review the PR.

Thanks