ESLint flat config is silently dropped

[yusuke99]

Describe the bug

When a project has ESLint flat config and uses vp migrate it drops unsupported rules, but it doesn't show any warning or report. In this situation, this would mislead that every ESLint rules was migrated successfully. Instead, show the report that was generated by @oxlint/migrate which is called under the hood by vp migrate.

Reproduction

https://github.com/yusuke99/vite-plus-reproduction/tree/migrate-eslint-rules-silent

Steps to reproduce

git clone --single-branch --branch migrate-eslint-rules-silent https://github.com/yusuke99/vite-plus-reproduction.git
cd vite-plus-reproduction
pnpm run vp-migrate

System Info

vp: 0.3.1
Node.js: 22.18.0
pnpm: 11.25.0

Used Package Manager

pnpm

Logs

Validations

• Read the Contributing Guidelines.
• Check that there isn't already an issue for the same bug.
• Confirm this is a Vite+ issue and not an upstream issue (Vite, Vitest, tsdown, Rolldown, or Oxc).
• The provided reproduction is a minimal reproducible example.