CRAFT [FEC] -2082 - Update to eslint9

[valoriecarli]

Migrate to ESLint 9 flat config

Migrates the root workspace from ESLint 8 legacy config to ESLint 9 flat config, following the migration guide shipped with @commercetools-frontend/eslint-config-mc-app@27.0.0.

Changes:

• Replaced .eslintrc.js + eslintignore with eslint.config.js (ignore patterns inlined, overrides converted to flat config objects)
• Bumped eslint 8.x → ^9.0.0 and eslint-config-mc-app to 27.0.0
• Removed cliOptions.rules from jest-runner-eslint.config.js - not supported in flat config mode; both rules were already covered by the base config
• Added globals.jest for **/*.visualspec.js and **/*.bundlespec.js - the base config only injects Jest globals for
  *.{spec,test}.*
• Removed stale @typescript-eslint/no-empty-function eslint-disable comments in test/setup-tests.js - @typescript-eslint is not registered for .js files in flat config, making those comments invalid

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Project	Deployment	Actions	Updated (UTC)
ui-kit	Ready	Preview, Comment	Mar 13, 2026 3:38pm

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