Install eslint, @eslint/js, and typescript-eslint as dev dependencies.
Add eslint.config.js (flat config) with rules tuned to zero errors on
the current codebase, add ESLint local hook to .pre-commit-config.yaml,
and update the lint:ts npm script to use ESLint directly.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
