refactor(migrate): drop @nuxt/eslint from ESLINT_ECOSYSTEM_NAMES

The entry was unreachable: when `@nuxt/eslint` is present anywhere in
the workspace, `detectIncompatibleEslintIntegration` short-circuits
the entire ESLint migration before `rewriteEslintPackageJson` runs,
so the second list never gets consulted. Two side effects from
keeping it duplicated:

- Maintenance hazard: the "what to do about Nuxt" decision lives in
  two places that could drift.
- Misleading future intent: a contributor scanning the cleanup list
  would conclude `@nuxt/eslint` gets stripped on migration, which
  isn't true today.

The right home for the policy is `INCOMPATIBLE_ESLINT_INTEGRATIONS`
(which is already what controls the actual behavior). Added an
explicit unit test asserting `rewriteEslintPackageJson` leaves
`@nuxt/eslint` alone, with a comment explaining the upstream skip.

Author: fengmk2

packages/cli/src/migration/__tests__/migrator.spec.ts

@@ -404,7 +404,7 @@ describe('rewriteEslintPackageJson', () => {
     expect(pkg.devDependencies).toEqual({ keepme: '^1.0.0' });
   });
 
-  it('removes ESLint formatter, helper, and runtime-integration packages', () => {
+  it('removes ESLint formatter and helper packages', () => {
     const pkgPath = writePkg({
       devDependencies: {
         eslint: '^9.0.0',
@@ -416,7 +416,6 @@ describe('rewriteEslintPackageJson', () => {
         'eslint-scope': '^8.0.0',
         'eslint-define-config': '^2.0.0',
         'eslint-doc-generator': '^2.0.0',
-        '@nuxt/eslint': '^0.5.0',
         keepme: '^1.0.0',
       },
     });
@@ -425,6 +424,21 @@ describe('rewriteEslintPackageJson', () => {
     expect(pkg.devDependencies).toEqual({ keepme: '^1.0.0' });
   });
 
+  it('does NOT remove framework-ESLint integrations (e.g. @nuxt/eslint) — those short-circuit migration upstream', () => {
+    // The skip path in `bin.ts` prevents `rewriteEslintPackageJson` from
+    // being called when `@nuxt/eslint` is present, so this function
+    // doesn't need to (and shouldn't) know about it.
+    const pkgPath = writePkg({
+      devDependencies: {
+        eslint: '^9.0.0',
+        '@nuxt/eslint': '^1.0.0',
+      },
+    });
+    rewriteEslintPackageJson(pkgPath);
+    const pkg = readJson(pkgPath);
+    expect(pkg.devDependencies).toEqual({ '@nuxt/eslint': '^1.0.0' });
+  });
+
   it('preserves reusable @typescript-eslint/* AST libraries (utils, typescript-estree, etc.)', () => {
     const pkgPath = writePkg({
       devDependencies: {

packages/cli/src/migration/migrator.ts

@@ -383,8 +383,11 @@ const ESLINT_ECOSYSTEM_NAMES = new Set<string>([
   '@typescript-eslint/eslint-plugin',
   '@typescript-eslint/parser',
   '@typescript-eslint/rule-tester',
-  // Framework runtime modules that wire ESLint and break without it:
-  '@nuxt/eslint',
+  // Note: framework-ESLint integration modules (e.g. `@nuxt/eslint`)
+  // are NOT listed here. They short-circuit the entire ESLint
+  // migration via `INCOMPATIBLE_ESLINT_INTEGRATIONS`, so this list is
+  // never consulted for them. Keeping them out avoids duplicating the
+  // "what to do about Nuxt" decision in two places.
 ]);
 
 // Flat name prefixes that mark an ESLint-only package.