[add] HTML Editor component with Edkit & Shadcn UI

[Copilot]

Ported the rich text editor from Edkit React to use Shadcn UI instead of Bootstrap.

Implementation

• Editor Component: ContentEditable-based editor with MobX state management, integrated with Edkit's @editor decorator
• Tool System:
  • Text formatting (bold, italic, underline, strikethrough, headings, font size, sub/superscript, links)
  • Color pickers for foreground/background colors
  • Layout tools (alignment, lists, horizontal rules)
  • Media insertion (images, audio, video, iframes)
  • Control operations (undo, redo, reset, clear)
  • Markdown export
• UI Migration: Replaced Bootstrap buttons with Shadcn UI Button components, mapped Bootstrap Icons to Lucide React
• Registry Entry: Component installable via npx shadcn-helper add https://mobx-restful-shadcn.idea2.app/r/editor.json

Usage

import { Editor, OriginalTools, ExtraTools } from "@/components/ui/editor";

<Editor
  tools={[...OriginalTools, ...ExtraTools]}
  name="content"
  defaultValue="Hello <b>Edkit</b>!"
  onChange={console.log}
/>

Screenshot

The toolbar displays all formatting options with Shadcn UI styling. Color pickers use native HTML color inputs overlaid with styled buttons.

Original prompt

基于 Shadcn UI 基础组件重新实现 https://github.com/idea2app/Edkit/tree/master/React

Human changes

1. [optimize] simplify Copilot's source codes
2. [remove] Example components

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