将 PDF 成品阅读控制器下沉为 RDPDFReaderView SDK，并修复手机横屏单页连续竖滑

SDK 化收尾：
- 新增 RDPDFReaderView 本地 pod（阅读容器、成品控制器、划线/注释、画笔、
  目录/设置面板、主题与持久化契约），Demo 精简为 PDFKit 页面提供者 + 持久化宿主
- Podfile/工程接入 RDPDFReaderView 与 SnapKit，示例书改用 PDF 阅读器示例文件

手机横屏单页竖滑修复：
- cell 高度改为宽度适配后的纸张高度（sizeForItemAt + 宿主按页提供纵横比），
  纵向超出一屏的内容由外层 collectionView 连续滚动承接，不再被裁掉
- 页面内部不再开启同向嵌套的兜底竖向拖动，修复外层滚动被吞、无法滚到下一页
- 修复 applyContentSize 先评估拖动开关后写 contentSize 的顺序缺陷
- 页码按视口中心命中 cell 计算，补 didEndDragging 兜底；旋转重锚点与
  transitionToPage 改用真实布局位置
- 横竖屏同为竖滑时也重建 cell 并刷新全部可见页的适配配置
- 横屏单页点击不再跳页，只显隐工具栏；翻页交给连续竖滑

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

ReadViewDemo/ReadViewDemoUITests/Helpers/XCUIApplication+Launch.swift

@@ -1,6 +1,19 @@
 import XCTest
 
 extension XCUIApplication {
+    func launchAndOpenSamplePDF(
+        bookTitleQuery: String = "PDF阅读器示例",
+        resetsReaderState: Bool = true,
+        pdfTextSource: String? = nil
+    ) {
+        launchAndOpenSampleBook(
+            bookTitleQuery: bookTitleQuery,
+            displayType: "pagecurl",
+            resetsReaderState: resetsReaderState,
+            pdfTextSource: pdfTextSource
+        )
+    }
+
     func launchAndOpenSampleBook(
         bookTitleQuery: String = "回归验证样本",
         displayType: String? = nil,
@@ -12,7 +25,8 @@ extension XCUIApplication {
         corruptsCache: Bool = false,
         allowsInspectableWebViews: Bool = false,
         enablesVerboseWebLogs: Bool = false,
-        searchKeyword: String? = nil
+        searchKeyword: String? = nil,
+        pdfTextSource: String? = nil
     ) {
         var args = ["--demo-book-title", bookTitleQuery]
         if resetsReaderState {
@@ -45,6 +59,9 @@ extension XCUIApplication {
         if let searchKeyword {
             args += ["--demo-search-keyword", searchKeyword]
         }
+        if let pdfTextSource {
+            args += ["--demo-pdf-text-source", pdfTextSource]
+        }
         launchArguments = args
         launch()
     }
@@ -74,7 +91,7 @@ extension XCUIApplication {
 
         let deadline = Date().addingTimeInterval(timeout)
         while Date() < deadline {
-            let content = otherElements[IDs.readerContent]
+            let content = otherElements[IDs.readerContent].firstMatch
             if content.waitForExistence(timeout: 1) {
                 content.coordinate(withNormalizedOffset: CGVector(dx: 0.5, dy: 0.5)).tap()
             } else {
@@ -92,7 +109,7 @@ extension XCUIApplication {
         for _ in 0..<3 {
             guard buttons[IDs.readerBack].exists else { return }
 
-            let content = otherElements[IDs.readerContent]
+            let content = otherElements[IDs.readerContent].firstMatch
             if content.waitForExistence(timeout: 2) {
                 content.coordinate(withNormalizedOffset: CGVector(dx: 0.5, dy: 0.6)).tap()
             }
@@ -139,7 +156,7 @@ extension XCUIApplication {
                 return selectionText
             }
 
-            let content = otherElements[IDs.readerContent]
+            let content = otherElements[IDs.readerContent].firstMatch
             if content.exists {
                 content.coordinate(withNormalizedOffset: CGVector(dx: 0.5, dy: 0.5)).tap()
             }