linting-neostandard-eslint9

Configures ESLint v9 flat config and neostandard for JavaScript and TypeScript projects, including migrating from legacy .eslintrc* files or the standard package. Use when you need to set up or fix linting with eslint.config.js or eslint.config.mjs, troubleshoot lint errors, configure neostandard rules, migrate from .eslintrc to flat config, or integrate linting into CI pipelines and pre-commit hooks.