CRAFT-2074: eslint9 migration

[valoriecarli]

ESLint 9 Flat Config Migration

⚠️ Do not merge as-is. The vendor/commercetools-frontend-eslint-config-mc-app-26.0.0.tgz tarball is committed temporarily for CI. Once the appkit PR lands and the package is published, replace the file:./vendor/... reference in package.json with the versioned npm reference & delete the tarball + vendor/ directory.

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What changed

Migrated from ESLint 8 legacy config (.eslintrc.js) to ESLint 9 flat config (eslint.config.js) following the MIGRATION.md guide shipped with @commercetools-frontend/eslint-config-mc-app@26.0.0.

Standard migration steps (per guide):

• Removed .eslintrc.js and .eslintignore
• Created eslint.config.js and spreads mcAppConfig, converts overrides to flat config objects, converts .eslintignore patterns to ignores array
• Bumped eslint 8.x → ^9.0.0 and eslint-config-mc-app to 26.0.0

UI-KIT specific:

• Added globals.jest + puppeteer globals (page, HOST) for **/*.visualspec.js. The base config only injects jest globals for *.{spec,test}.js
• Added globals.jest for **/*.bundlespec.js, same as above
• Removed stale eslint-disable inline comments in test/setup-tests.js and packages/utils/src/warning.ts that referenced plugins not registered for those file types in flat config
• Removed generators/ from ignores and fixed pre-existing violations that were previously hidden: import/first ordering in generator bin files, unused catch binding in generators/readme/src/index.ts, and inlineCode function hoisting
• Added generators/readme/test/ to ignores. Test fixtures use fake package names that don't resolve
• Updated jest-runner-eslint.config.js formatter from stylish → eslint-formatter-pretty

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Project	Deployment	Actions	Updated (UTC)
ui-kit	Ready	Preview, Comment	Feb 18, 2026 5:07pm

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