Json Render React Email

# @json-render/react-email

React Email renderer that converts JSON specs into HTML or plain-text email output.

## Quick Start

```typescript
import { renderToHtml } from "@json-render/react-email";
import { schema, standardComponentDefinitions } from "@json-render/react-email";
import { defineCatalog } from "@json-render/core";

const catalog = defineCatalog(schema, {
  components: standardComponentDefinitions,
});

const spec = {
  root: "html-1",
  elements: {
    "html-1": { type: "Html", props: { lang: "en", dir: "ltr" }, children: ["head-1", "body-1"] },
    "head-1": { type: "Head", props: {}, children: [] },
    "body-1": {
      type: "Body",
      props: { style: { backgroundColor: "#f6f9fc" } },
      children: ["container-1"],
    },
    "container-1": {
      type: "Container",
      props: { style: { maxWidth: "600px", margin: "0 auto", padding: "20px" } },
      children: ["heading-1", "text-1"],
    },
    "heading-1": { type: "Heading", props: { text: "Welcome" }, children: [] },
    "text-1": { type: "Text", props: { text: "Thanks for signing up." }, children: [] },
  },
};

const html = await renderToHtml(spec);
```

## Spec Structure (Element Tree)

Same flat element tree as `@json-render/react`: `root` key plus `elements` map. Root must be `Html`; children of `Html` should be `Head` and `Body`. Use `Container` (e.g. max-width 600px) inside `Body` for client-safe layout.

## Creating a Catalog and Registry

```typescript
import { defineCatalog } from "@json-render/core";
import { schema, defineRegistry, renderToHtml } from "@json-render/react-email";
import { standardComponentDefinitions } from "@json-render/react-email/catalog";
import { Container, Heading, Text } from "@react-email/components";
import { z } from "zod";

const catalog = defineCatalog(schema, {
  components: {
    ...standardComponentDefinitions,
    Alert: {
      props: z.object({
        message: z.string(),
        variant: z.enum(["info", "success", "warning"]).nullable(),
      }),
      slots: [],
      description: "A highlighted message block",
    },
  },
  actions: {},
});

const { registry } = defineRegistry(catalog, {
  components: {
    Alert: ({ props }) => (
      <Container style={{ padding: 16, backgroundColor: "#eff6ff", borderRadius: 8 }}>
        <Text style={{ margin: 0 }}>{props.message}</Text>
      </Container>
    ),
  },
});

const html = await renderToHtml(spec, { registry });
```

## Server-Side Render APIs

| Function | Purpose |
|----------|---------|
| `renderToHtml(spec, options?)` | Render spec to HTML email string |
| `renderToPlainText(spec, options?)` | Render spec to plain-text email string |

`RenderOptions`: `registry`, `includeStandard` (default true), `state` (for `$state` / `$cond`).

## Visibility and State

Supports `visible` conditions, `$state`, `$cond`, repeat (`repeat.statePath`), and the same expression syntax as `@json-render/react`. Use `state` in `RenderOptions` when rendering server-side so expressions resolve.

## Server-Safe Import

Import schema and catalog without React or `@react-email/components`:

```typescript
import { schema, standardComponentDefinitions } from "@json-render/react-email/server";
```

## Key Exports

| Export | Purpose |
|--------|---------|
| `defineRegistry` | Create type-safe component registry from catalog |
| `Renderer` | Render spec in browser (e.g. preview); use with `JSONUIProvider` for state/actions |
| `createRenderer` | Standalone renderer com