fix!: remove rollup, extraneous types and migrate to ESM-only

[lumirlumir]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

In this PR, I've resolved the issue mentioned in #196, removing rollup and extraneous types and migrating the package to ESM-only.

The main focus of this PR is removing much of the logic and the workarounds we previously used to support a dual CommonJS/ESM package.

Some notable parts are as follows:

• tsconfig.json: I mostly followed the convention used in the Markdown plugin, which is now an ESM-only package. (Ref: https://github.com/eslint/markdown/blob/main/tsconfig.json)
• package.json: Likewise, I mostly followed the convention used in the Markdown plugin. (Ref: https://github.com/eslint/markdown/blob/main/package.json)
• .github/workflows/ci.yml: Added @arethetypeswrong/cli to verify that type exports work correctly.

What changes did you make? (Give an overview)

In this PR, I've resolved the issue mentioned in #196, removing rollup and extraneous types and migrating the package to ESM-only.

Related Issues

• Counterpart: fix!: remove rollup, extraneous types and migrate to ESM-only css#352
• Prior Arts:
  • fix!: remove rollup and extraneous types markdown#383
  • ci: run arethetypeswrong in CI markdown#598
• Closes: Change Request: Remove rollup and migrate to ESM-only as part of the upcoming v1.0.0 (JSON/CSS) #196

Is there anything you'd like reviewers to focus on?

I didn't intentionally remove tests/types/cjs-import.test.cts since require(ESM) is now enabled. However, if removing it is the right course of action, I'm happy to do so.

[lumirlumir]

README.md pre-commit hook update can be consolidated into a single line, I went ahead. Just for a reference, the Markdown plugin also uses this approach:

Ref: https://github.com/eslint/markdown/blob/main/package.json#L56-L59

[Copilot]

Pull request overview

This PR migrates the @eslint/json package from a dual CommonJS/ESM format to ESM-only, removing the Rollup bundler and associated build complexity. The migration simplifies the build process by eliminating workarounds previously needed to support both module formats.

Key changes:

• Replaced Rollup-based bundling with TypeScript compilation that emits both JavaScript and declaration files
• Simplified package.json exports to use a single ESM entry point instead of dual CJS/ESM conditional exports
• Updated all internal type imports from .ts to .js extensions to comply with ESM module resolution

Reviewed changes

Copilot reviewed 14 out of 15 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tsconfig.json	Simplified TypeScript configuration for ESM-only output, removing dual-format compilation settings and consolidating output to single dist/ directory
tsconfig.esm.json	Removed secondary TypeScript configuration file that was used for ESM-specific type generation
tools/dedupe-types.js	Removed script that deduped type imports after rollup bundling, no longer needed without rollup
tools/build-cts.js	Removed script that generated CommonJS type definitions (.cts files), no longer needed for ESM-only package
rollup.config.js	Removed Rollup configuration and bundler from build process
package.json	Updated exports to ESM-only format, simplified build scripts, added @arethetypeswrong/cli for type validation, removed rollup dependencies, consolidated lint-staged configuration
src/rules/*.js	Updated type imports from ../types.ts to ../types.js to follow ESM conventions
src/languages/json-source-code.js	Updated type import from ../types.ts to ../types.js
jsr.json	Updated export paths and simplified publish configuration to reference consolidated dist/ directory
.github/workflows/ci.yml	Added new CI job to validate type definitions using @arethetypeswrong/cli

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