Add vitest config to prevent deploy side-effect

[Copilot]

vitest run falls back to vite.config.mts when no vitest.config.mts exists. This causes the markedit-copy-dist-file plugin's closeBundle hook to fire during test runs, printing "Successfully deployed to …" and copying files when a dist/ directory is present from a prior build.

• Add vitest.config.mts with only the define needed for __PKG_VERSION__ — no build/deploy plugins
• Revert the earlier build/precheck script split since the root cause was config inheritance, not script chaining

// vitest.config.mts — standalone, does not inherit vite.config.mts
import { defineConfig } from 'vitest/config';
import mainPackage from './package.json' with { type: 'json' };

export default defineConfig({
  define: {
    __PKG_VERSION__: JSON.stringify(mainPackage.version),
  },
});

[cyanzhong]

@copilot Is this file being used out of the box?

[Copilot]

Yes — vitest automatically discovers vitest.config.{ts,mts,js,...} in the project root before falling back to vite.config.*. No extra flags or package.json changes needed. The test script stays as vitest run and it picks up vitest.config.mts on its own.