fix(dpip): [PKG-DPIP-04] preserve factory type and export compatibility

packages/artplayer-plugin-document-pip/README.md

@@ -6,6 +6,59 @@ Document PIP plugin for ArtPlayer
 
 [https://artplayer.org](https://artplayer.org/?libs=./uncompiled/artplayer-plugin-document-pip/index.js&example=document.pip)
 
+## TypeScript and module formats
+
+```ts
+import Artplayer from 'artplayer'
+import type { AsyncResult } from 'artplayer-plugin-document-pip'
+import documentPip from 'artplayer-plugin-document-pip'
+
+const art = new Artplayer({
+  container: '#player',
+  url: 'video.mp4',
+  plugins: [documentPip({ width: 480, height: 270 })],
+})
+
+// Use this view for an unmodified plugin result when precise Promise types are needed.
+const pip = art.plugins.artplayerPluginDocumentPip as AsyncResult
+await pip.open()
+await pip.close()
+```
+
+At runtime, options may be omitted. Width and height default to 480 and 270, and
+`fallbackToVideoPiP` defaults to true. `placeholder` sets the text left in the
+original player container while its document window is active.
+
+The default `Result` retains the published writable boolean fields and void
+actions so old assignments and inferred initializer types still compile.
+At runtime, `isSupported` and `isActive` are readonly getters, `open` and `close`
+return `Promise<void>`, and `toggle` returns `undefined`. The opt-in `AsyncResult`
+describes those runtime values; it should not be applied to a mock or a result
+whose methods have been replaced. It does not change any runtime behavior.
+
+The default factory declaration keeps the exact published required-argument
+signature, including assignment of an old replacement function to `typeof
+documentPip`. Automatically adding an optional overload or a required `.default`
+property would break such assignments. `Option`, `Result`, `AsyncResult`, `Factory`
+and `RuntimeFactory` are available as named types. Use the explicit runtime view
+to type omitted options, self `.default` access and precise async results:
+
+```ts
+import type { RuntimeFactory } from 'artplayer-plugin-document-pip'
+const runtimeFactory = documentPip as RuntimeFactory
+runtimeFactory() // precise initializer for the unmodified runtime factory
+```
+
+ESM uses the default import. CommonJS supports both `require(package)(options)`
+and the historical `require(package).default(options)` shape; `.default` is the
+same factory. The `/legacy` entry and generated browser editor declarations have
+matching types. These syntax targets do not add native Document PiP support to
+browsers that lack the API.
+
+The historical TypeScript `import plugin = require(package)` module view retains
+`plugin.default(options)`. Direct CommonJS calls are available at runtime; use
+`RuntimeFactory` for an explicitly typed direct-call view.
+
 ## Maintenance
 
 Source is split into strict TypeScript modules for window ownership, DOM migration,