fix(canvas): [PKG-CANVAS-04] preserve public type and export compatibility

packages/artplayer-proxy-canvas/README.md

@@ -2,6 +2,52 @@
 
 canvas proxy for ArtPlayer
 
+## Usage
+
+```js
+import Artplayer from 'artplayer'
+import canvas from 'artplayer-proxy-canvas'
+
+const art = new Artplayer({
+  container: '#player',
+  url: 'video.mp4',
+  proxy: canvas((context, video) => {
+    // Post-process the frame with the native 2D context.
+  }),
+})
+```
+
+The callback is optional. Registration returns a native Canvas synchronously. Its own
+methods and properties keep Canvas behavior; video-only enumerable properties are
+forwarded to the backing video. Use ArtPlayer's `video:*` events for media notifications.
+The callback receives the actual video, and a successful callback is followed by
+`artplayerProxyCanvas:draw`. Drawing failures emit `artplayerProxyCanvas:error`.
+
+ES modules use the default import. Both `require('artplayer-proxy-canvas')` and the
+historical `require('artplayer-proxy-canvas').default` refer to the same factory. The
+`artplayer-proxy-canvas/legacy` entry preserves the legacy browser build.
+
+## TypeScript
+
+The optional callback and exact `HTMLCanvasElement` return type retain published 1.1.0
+inference. `Option`, `Result`, `Factory` and `MediaCanvas` are exported types. The last is
+an explicit view for code using supported forwarded media members:
+
+```ts
+import type { MediaCanvas, Option } from 'artplayer-proxy-canvas'
+
+const callback: Option = (context, video) => context.drawImage(video, 0, 0)
+const media = art.template.$video as MediaCanvas
+await media.play()
+```
+
+`MediaCanvas` keeps Canvas members when names overlap, including dimensions and DOM
+listeners. It does not add unsupported browser APIs. Factory return inference remains
+`HTMLCanvasElement`, so existing assignments and `ReturnType` consumers keep compiling.
+Runtime falsy callback arguments retain historical behavior; declarations accept an
+optional function, matching the published types. Implementation and test guidance is in
+[ARCHITECTURE.md](ARCHITECTURE.md).
+
 ## Demo
 
 [https://artplayer.org](https://artplayer.org/?libs=./uncompiled/artplayer-proxy-canvas/index.js&example=canvas)