docs(usage): document el helper and type namespace 🍷

- Add API table row and section Helper (el) with example and el.root, el.node, tag aliases
- Document default export as callable with create, render, el and Types namespace import
- Add Schema2UIDefaultExport to type reference and update tests list

Author: NeaByteLab

USAGE.md

@@ -7,6 +7,7 @@ API, node shape, layout and style — create schema from definition, render to D
 - [Quick Start](#quick-start)
 - [Flow Overview](#flow-overview)
 - [API Overview](#api-overview)
+- [Helper (el)](#helper-el)
 - [Node Shape](#node-shape)
 - [Layout and Style](#layout-and-style)
 - [Void Tags and Special Elements](#void-tags-and-special-elements)
@@ -41,12 +42,40 @@ render(schema, document.getElementById('app'))
 
 ## API Overview
 
-| Function / export                                      | Returns  | Description                                    |
-| :----------------------------------------------------- | :------- | :--------------------------------------------- |
-| [`create(definition)`](#createdefinition)              | `Schema` | Validate and freeze definition; return schema. |
-| [`render(schema, container)`](#renderschema-container) | `void`   | Build DOM from schema and append to container. |
+| Function / export                                      | Returns   | Description                                    |
+| :----------------------------------------------------- | :-------- | :--------------------------------------------- |
+| [`create(definition)`](#createdefinition)              | `Schema`  | Validate and freeze definition; return schema. |
+| [`render(schema, container)`](#renderschema-container) | `void`    | Build DOM from schema and append to container. |
+| `el`                                                   | namespace | Helper: `el.root`, `el.node`, `el.div`, etc.   |
 
-Named exports: `create`, `render`, and all types from `Types` (re-exported). Default export: `{ create, render }`.
+Named exports: `create`, `render`, `el`, and `Types` (re-exported). Default export: callable; calling it returns `{ create, render, el }`, and the callable itself has `.create`, `.render`, `.el` for direct use (e.g. `import Schema2UI from '@neabyte/schema2ui'` then `Schema2UI().create(...)` or `Schema2UI.create(...)`).
+
+## Helper (el)
+
+Use the `el` namespace to build definitions with less boilerplate. Same flow: `create(el.root(...))` → schema → `render(schema, container)`.
+
+```typescript
+// 1. Import create, render, and the el helper
+import { create, render, el } from '@neabyte/schema2ui'
+
+// 2. Build definition with el.root(...), pass to create() to get frozen schema (tag aliases: el.header, el.main, el.h1, el.a)
+const schema = create(
+  el.root(
+    el.header(
+      { id: 'header', layout: { width: '100%', height: 56 }, style: { fill: '#1a1a2e' } },
+      el.h1({ id: 'title', style: { font: '20px sans-serif', fill: '#eee' } }, 'Hello')
+    ),
+    el.main({ layout: { width: '100%', flex: 1 } }, el.a({ attrs: { href: '/' } }, 'Home'))
+  )
+)
+
+// 3. Render schema into the container element
+render(schema, document.getElementById('app'))
+```
+
+- **`el.root()`** — returns `Definition` with empty `root: []`. **`el.root(n1, n2, ...)`** or **`el.root([n1, n2])`** — returns `Definition` for `create()`.
+- **`el.node(type, propsOrContent?, ...rest)`** — generic factory (e.g. custom elements). Second arg: optional props object, text content, or first child; `rest`: more children or content. Content (string) and children cannot be mixed. Void tags must not have content or children.
+- **Tag aliases** — `el.div`, `el.span`, `el.main`, `el.header`, `el.h1`, `el.a`, `el.table`, `el.img`, `el.template`, etc. (container + void from `Constant.tagAliases`). Container tags accept props, content (string), or children (nodes). Void tags (img, br, input, …) accept props only.
 
 ## Node Shape
 
@@ -98,16 +127,17 @@ Build DOM from `schema.root` and append each resulting node into `container`. Us
 
 ## Type Reference
 
-Types are re-exported from the package: `import type { Attrs, Definition, Layout, Node, Schema, Style } from '@neabyte/schema2ui'`.
+Types are re-exported under the `Types` namespace: `import type * as Types from '@neabyte/schema2ui'` then use `Types.Node`, `Types.Schema`, `Types.Attrs`, etc.
 
 - **Definition:** `{ root: readonly Node[] }` — Input to `create`.
 - **Schema:** `{ readonly root: readonly Node[] }` — Output of `create`; frozen.
 - **Node:** Object with `type` (string) and optional `id`, `layout`, `style`, `attrs`, `content`, `src`, `alt`, `children` (readonly array of Node). Void tags must not have `children`.
 - **Layout:** Optional `width`, `height`, `x`, `y`, `flex`, `gap` — each `number | string`.
 - **Style:** Optional `border`, `borderRadius`, `boxShadow`, `color`, `fill`, `font`, `margin`, `opacity`, `padding`, `stroke`, `transition` — each `string`.
 - **Attrs:** `Record<string, string | number | boolean>` — HTML attributes. Special handling for `class`/`className`, `style` (string), `value`, `checked`, `disabled` on form elements.
+- **Schema2UIDefault:** `{ create, render }` — shape returned when calling the default export. **Schema2UIDefaultExport:** callable with `.create`, `.render`, `.el`; calling it returns `Schema2UIDefault & { el: El }`.
 
 ## Reference
 
 - [README](README.md) — Installation and quick start.
-- Tests under `tests/` — Create, Constant, Validator, Render.
+- Tests under `tests/` — Constant, Create, Helper, Index, Render, Validator.