feat!: Remove Tailwind syntax in favor of external tailwind-csstree

[nzakas]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

Updated Tailwind support recommend using the tailwind-csstree package that I wrote on my own time. It covers Tailwind 3 and 4 and is much more robust than what we had in this plugin.

What changes did you make? (Give an overview)

• Updated README to recommend installing tailwind-csstree
• Removed the /syntax entrypoint from package.json and jsr.json
• Removed build scripts for /syntax
• Removed source code for /syntax

Related Issues

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

[eslint-github-bot]

Hi @nzakas!, thanks for the Pull Request

The pull request title isn't properly formatted. We ask that you update the pull request title to match this format, as we use it to generate changelogs and automate releases.

• The length of the commit message must be less than or equal to 72

To Fix: You can fix this problem by clicking 'Edit' next to the pull request title at the top of this page.

Read more about contributing to ESLint here

[Copilot]

Pull Request Overview

This PR removes the built-in Tailwind CSS syntax support and updates the plugin to rely on the external tailwind-csstree package.

• Eliminates internal /syntax source, build configs, and TS configs
• Updates tests and docs to import tailwind-csstree instead of the removed tailwindSyntax
• Cleans up package exports, build scripts, and dependencies

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tsconfig.syntax.json	Removed TS config for internal syntax output
tests/rules/no-invalid-at-rules.test.js	Switched customSyntax imports from internal to tailwind3
src/syntax/tailwind-syntax.js	Deleted internal Tailwind syntax definitions
src/syntax/index.js	Removed re-export of tailwindSyntax
rollup.config.js	Dropped the syntax bundle configuration
package.json	Removed syntax entrypoint, adjusted build scripts, added dependency
jsr.json	Removed ./syntax export
README.md	Updated docs to install and import from tailwind-csstree

Comments suppressed due to low confidence (2)

README.md:233

• The README example imports tailwind4 but tests and the package use tailwind3. Update the example to match the actual export (e.g. tailwind3) or clarify version support.

import { tailwind4 } from "tailwind-csstree";

package.json:106

• [nitpick] Consider moving tailwind-csstree from devDependencies to peerDependencies so that consumers explicitly install a compatible version rather than relying on your dev setup.

"tailwind-csstree": "^0.1.0",

[fasttime]

LGTM, thanks! Leaving open for a second review.