Ship ESM and CommonJS builds so packages are importable by bundlers

[Copilot]

Packages only shipped an IIFE (browser-global) bundle, so import Yasgui from '@matdata/yasgui' failed in Vite/webpack/esbuild despite the docs advertising it.

Changes

• esbuild.config.js — Each package now emits three JS bundles instead of one: ESM (*.mjs), CommonJS (*.cjs), and the existing browser-global IIFE (*.min.js). A single canonical *.min.css is retained (all three JS bundles import identical styles; extracted extractCss/removeExtraCss helpers handle this).
• packages/*/package.json (all 4) — Added main (CJS), module (ESM), unpkg/jsdelivr (global), and a conditional exports map with import/require/types/default plus CSS and ./build/* subpaths.
• Extensions — Used .mjs/.cjs rather than .esm.js/.cjs.js: files under build/ inherit the root "type": "module", making bare .js ambiguous to Node. Explicit extensions guarantee correct format resolution in every consumer.
• Docs / changeset — CommonJS example corrected to require('@matdata/yasgui').default (esbuild places the default under .default); minor changeset added for all four packages.

// ESM (bundlers / Node import)
import Yasgui from '@matdata/yasgui';
import '@matdata/yasgui/build/yasgui.min.css';

// CommonJS
const Yasgui = require('@matdata/yasgui').default;

Existing <script src=".../build/yasgui.min.js"> global usage is preserved via unpkg/jsdelivr.

• Fixes npm build has no module exports, so it can't be imported with a bundler #185

[Copilot]

Copilot review overview

🟡 Changes recommended

The review identified packaging/build issues that can mislead consumers (Node engine constraints) and potentially break sourcemap correctness for renamed CSS outputs.

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Review effort: Lite
Findings: 1 · 2

Open (3)

• Renamed CSS output leaves source map path stale · New
• Node engine constraint is too low for conditional exports · New
• Node engine constraint is too low for conditional exports · New

What changed in this PR

This PR updates MatGUI’s build and package metadata so the published npm artifacts are importable by bundlers and Node consumers (ESM/CJS), while preserving the existing browser-global IIFE distribution for <script> usage—addressing issue #185.

Changes:

• Extend the esbuild pipeline to emit ESM (.mjs), CJS (.cjs), and IIFE (.min.js) bundles per package while keeping a single canonical CSS output.
• Update each package’s package.json to expose main/module/unpkg/jsdelivr and a conditional exports map for import/require/types/default (plus CSS/build subpaths where relevant).
• Add a regression unit test that validates the packed tarball’s structure and verifies ESM/CJS resolution and a Vite build consumer.

File	Description
esbuild.config.js	Builds per-package ESM/CJS/IIFE outputs and manages a single canonical CSS artifact.
packages/​yasgui/​package.json	Adds main/module/exports/CDN fields so bundlers and Node can resolve the package correctly.
packages/​yasqe/​package.json	Adds main/module/exports/CDN fields so bundlers and Node can resolve the package correctly.
packages/​yasr/​package.json	Adds main/module/exports/CDN fields so bundlers and Node can resolve the package correctly.
packages/​utils/​package.json	Adds main/module/exports/CDN fields so bundlers and Node can resolve the package correctly.
test/​unit/​package-consumption-test.ts	Regression test that exercises npm pack output and validates ESM/CJS resolution and Vite bundling.
docs/​developer-guide.md	Updates CommonJS usage to access the default export via .default.
.changeset/​esm-module-exports.md	Records a minor release note describing the new ESM/CJS publishing behavior.

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