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>

Sources/RDEpubReaderView/EPUBUI/RDEPUBAnnotationEditorViewController.swift

@@ -1,4 +1,5 @@
 import UIKit
+import SnapKit
 
 final class RDEPUBAnnotationEditorViewController: UIViewController, UITextViewDelegate {
 
@@ -56,9 +57,6 @@ final class RDEPUBAnnotationEditorViewController: UIViewController, UITextViewDe
         let quoteLabel = UILabel()
         let inputCard = UIView()
 
-        [quoteCard, rail, quoteLabel, inputCard, textView, countLabel].forEach {
-            $0.translatesAutoresizingMaskIntoConstraints = false
-        }
         view.addSubview(quoteCard)
         quoteCard.addSubview(rail)
         quoteCard.addSubview(quoteLabel)
@@ -91,32 +89,34 @@ final class RDEPUBAnnotationEditorViewController: UIViewController, UITextViewDe
         countLabel.textColor = .secondaryLabel
         countLabel.textAlignment = .right
 
-        NSLayoutConstraint.activate([
-            quoteCard.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 20),
-            quoteCard.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
-            quoteCard.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20),
-            rail.leadingAnchor.constraint(equalTo: quoteCard.leadingAnchor, constant: 16),
-            rail.topAnchor.constraint(equalTo: quoteCard.topAnchor, constant: 16),
-            rail.bottomAnchor.constraint(equalTo: quoteCard.bottomAnchor, constant: -16),
-            rail.widthAnchor.constraint(equalToConstant: 4),
-            quoteLabel.leadingAnchor.constraint(equalTo: rail.trailingAnchor, constant: 14),
-            quoteLabel.trailingAnchor.constraint(equalTo: quoteCard.trailingAnchor, constant: -18),
-            quoteLabel.topAnchor.constraint(equalTo: quoteCard.topAnchor, constant: 16),
-            quoteLabel.bottomAnchor.constraint(equalTo: quoteCard.bottomAnchor, constant: -16),
-
-            inputCard.topAnchor.constraint(equalTo: quoteCard.bottomAnchor, constant: 18),
-            inputCard.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
-            inputCard.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20),
-            inputCard.bottomAnchor.constraint(equalTo: view.keyboardLayoutGuide.topAnchor, constant: -16),
-            inputCard.heightAnchor.constraint(greaterThanOrEqualToConstant: 210),
-            textView.topAnchor.constraint(equalTo: inputCard.topAnchor, constant: 14),
-            textView.leadingAnchor.constraint(equalTo: inputCard.leadingAnchor, constant: 14),
-            textView.trailingAnchor.constraint(equalTo: inputCard.trailingAnchor, constant: -14),
-            textView.bottomAnchor.constraint(equalTo: countLabel.topAnchor, constant: -8),
-            countLabel.leadingAnchor.constraint(equalTo: inputCard.leadingAnchor, constant: 16),
-            countLabel.trailingAnchor.constraint(equalTo: inputCard.trailingAnchor, constant: -16),
-            countLabel.bottomAnchor.constraint(equalTo: inputCard.bottomAnchor, constant: -12)
-        ])
+        quoteCard.snp.makeConstraints { make in
+            make.top.equalTo(view.safeAreaLayoutGuide).offset(20)
+            make.horizontalEdges.equalToSuperview().inset(20)
+        }
+        rail.snp.makeConstraints { make in
+            make.leading.equalToSuperview().offset(16)
+            make.verticalEdges.equalToSuperview().inset(16)
+            make.width.equalTo(4)
+        }
+        quoteLabel.snp.makeConstraints { make in
+            make.leading.equalTo(rail.snp.trailing).offset(14)
+            make.trailing.equalToSuperview().inset(18)
+            make.verticalEdges.equalToSuperview().inset(16)
+        }
+        inputCard.snp.makeConstraints { make in
+            make.top.equalTo(quoteCard.snp.bottom).offset(18)
+            make.horizontalEdges.equalToSuperview().inset(20)
+            make.bottom.equalTo(view.keyboardLayoutGuide.snp.top).offset(-16)
+            make.height.greaterThanOrEqualTo(210)
+        }
+        textView.snp.makeConstraints { make in
+            make.top.horizontalEdges.equalToSuperview().inset(14)
+            make.bottom.equalTo(countLabel.snp.top).offset(-8)
+        }
+        countLabel.snp.makeConstraints { make in
+            make.horizontalEdges.equalToSuperview().inset(16)
+            make.bottom.equalToSuperview().inset(12)
+        }
     }
 
     func textViewDidChange(_ textView: UITextView) {