fix(next-codemod): only bump eslint when it does not satisfy the eslint-config-next peer range - #98593

What?

@next/codemod upgrade no longer rewrites the project's eslint specifier
when it already satisfies the eslint-config-next peer range. A project on
eslint@^9 stays on ^9 instead of being pinned to the newest ESLint 10
release.

When a bump is still required (for example eslint@^8 against a >=9 peer),
the tool pins the highest release of the lowest major satisfying the peer
range, so projects land on the closest satisfying major instead of the newest
eslint release.

Fixes #98417

Why?

eslint-config-next@16 declares eslint: ">=9.0.0". The upgrade tool called
loadHighestNPMVersionMatching("eslint@>=9") and wrote the result as an exact
pin, so a project on ^9 got forced onto the newest ESLint 10 release. With
plugins that do not support ESLint 10 yet (e.g. eslint-plugin-import), the
post-upgrade npm install failed before any transformation ran, per the
linked issue's repro.

How did you fix it?

• New pure helper resolveEslintUpgradeTarget in bin/shared.ts. It returns
  null (leave the specifier untouched) when the installed specifier satisfies
  the peer range - including specifiers entirely above the peer minimum, so
  nothing gets downgraded - or when it cannot be interpreted as a semver range
  (latest, workspace/npm aliases). Otherwise it resolves the highest release
  of the lowest major satisfying the peer range through the injected resolver.
• bin/upgrade.ts uses the helper for the eslint alignment step. Behavior for
  projects below the peer range is unchanged except that the target is the
  lowest satisfying major rather than the newest release.
• Unit tests for the decision table in
  bin/__tests__/eslint-upgrade-target.test.ts.

How to test?

• pnpm test packages/next-codemod/bin/__tests__/eslint-upgrade-target.test.ts
• Or against the repro in @next/codemod upgrade pins ESLint to 10 unprompted, failing install for projects using eslint-plugin-import #98417: npx @next/codemod@canary upgrade latest
  on a create-next-app@15.5.0 project with eslint@^9 +
  eslint-plugin-import. The manifest keeps "eslint": "^9" and the install
  succeeds.