fix(cli): dynamically scan root .d.ts files from @vitest/browser

[kazupon]

Summary

• Replace hardcoded list of root .d.ts files with dynamic readdir scan for @vitest/browser package
• This ensures newly added type definition files (like aria-role.d.ts, utils.d.ts) are automatically included without requiring manual updates to the build script

related #909 in the TODO.

Test ways

• Run node --import @oxc-node/core/register ./build.ts in packages/test and verify only @vitest/browser root .d.ts files are copied (aria-role.d.ts, context.d.ts, jest-dom.d.ts, matchers.d.ts, utils.d.ts)
• Verify vp pack succeeds in a library project that imports UserConfig from vite-plus

[netlify]

👷 Deploy Preview for viteplus-preview processing.

Name	Link
🔨 Latest commit	7569be0
🔍 Latest deploy log	https://app.netlify.com/projects/viteplus-preview/deploys/69b7a4b9fc27e10008626809

[netlify]

✅ Deploy Preview for viteplus-preview canceled.

Name	Link
🔨 Latest commit	6941b1e
🔍 Latest deploy log	https://app.netlify.com/projects/viteplus-preview/deploys/69b7a60ba567a30008f886b4

[fengmk2]

@kazupon Thanks again! 💯