refactor!: ESM-only

[fb55]

• Set type: module, update tsconfig to nodenext
• Output to dist/ instead of lib/, remove dual CJS/ESM build
• Simplify exports to ESM-only
• Migrate Jest to Vitest
• Bump domelementtype to ^3.0.0
• Add engines >= 20.19.0
• Add publish workflow (npm + JSR)

BREAKING CHANGE: This package is now ESM-only.

[Copilot]

Pull request overview

This PR converts the package to ESM-only by switching the TypeScript build to NodeNext ESM output in dist/, updating package exports accordingly, and migrating the test runner from Jest to Vitest. It also modernizes CI/publishing workflows and updates runtime constraints/dependencies to match the new ESM + Node 20+ baseline.

Changes:

• Switch TS + package config to ESM-only (type: module, moduleResolution: nodenext, build output to dist/ with simplified exports)
• Migrate tests from Jest to Vitest and update ESM-incompatible test patterns (__dirname, require, import specifiers)
• Update CI/publish workflows and bump Node engine + dependency versions

Reviewed changes

Copilot reviewed 7 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tsconfig.json	Switch to NodeNext module settings and emit to dist/ for ESM-only output.
src/node.spec.ts	Update test imports for Vitest + ESM .js specifiers.
src/index.spec.ts	Replace CJS-only patterns (__dirname, require) with ESM equivalents and use Vitest APIs.
package.json	Set type: module, update build/test scripts, simplify exports to ESM-only, bump engines/deps, add Vitest.
biome.json	Update Biome schema reference.
.gitignore	Replace lib/ with dist/ and ignore generated jsr.json.
.github/workflows/publish.yml	Add tag-based publish workflow for npm + JSR (generates jsr.json).
.github/workflows/nodejs-test.yml	Update Node matrix and switch CI test execution to Vitest.
.github/workflows/codeql-analysis.yml	Minor workflow cleanup (comment removal).

Comments suppressed due to low confidence (1)

src/node.spec.ts:12

• The test name still references Jest ("Jest snapshot") after migrating to Vitest. Updating the wording will avoid confusion when reading test output or failures.

describe("Nodes", () => {
    it("should serialize to a Jest snapshot", () => {
        const result = parse(

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

You can also share your feedback on Copilot code review. Take the survey.