Closes: #910

Description

Bug: A recent script change ran ESLint without loading eslint.config.js. With ESLint 8, Flat Config is not auto-loaded, so linting appeared inactive/inconsistent.

Fix:

• Enable Flat Config explicitly for ESLint 8 using ESLINT_USE_FLAT_CONFIG=true (cross-platform via cross-env).
• Remove the legacy eslintConfig block from package.json to avoid accidental fallback to eslintrc.
• Keep the lint scope to assets/js/src/**/*.{js,jsx,ts,tsx} (as intended).

Changes

• package.json:
  • lint:js → cross-env ESLINT_USE_FLAT_CONFIG=true eslint "assets/js/src/**/*.{js,jsx,ts,tsx}"
  • remove eslintConfig block
  • (optional, unused) remove old "babel" config

No runtime code paths changed; tooling only.

How to test

1. rm -rf node_modules && npm ci
2. npm run lint:js
3. Expect ESLint to apply rules from eslint.config.js
4. If VS Code squiggles don’t appear immediately: Reload Window*.

Checklist

• Bug fix verified locally (npm run lint:js works again)
• Linked to ticket (add number above)
• [] CHANGELOG updated under Fixes / Tooling
• I want my code added to WP Rig