修复阅读器资源、朗读与持久化稳定性

阅读器在多会话朗读、加密 EPUB 资源、并发打开同一本书和多 UserDefaults 容器等场景下，存在旧异步结果覆盖新状态、锁屏控制串会话、大型明文资源被误拒绝、解压半成品被复用及标注跨容器混用的风险；同时高亮、书签、搜索和设置面板的空状态与自动化可访问性入口不完整。\n\n本次为朗读会话引入代次和当前 utterance 校验，远程控制改为仅响应当前会话并按自身 token 清理；加密资源 provider 先判定是否实际返回解密数据，明文大资源继续流式读取；解压缓存串行化以避免并发复用未完成目录。书签与高亮迁移至受保护文件，按 UserDefaults 容器隔离命名空间，保留标准容器旧文件兼容并确保新副本成功落盘后才删除历史数据。\n\n同步调整缓存淘汰、FoundationModels 弱链接、搜索/标注/设置面板交互与 UI 测试，并更新 Pod 生成配置及 API、风险文档。已执行 git diff --check 和 ReadViewDemo Debug Simulator 构建，结果为 BUILD SUCCEEDED。

Sources/RDEpubReaderView/EPUBUI/RDEPUBReaderHighlightsViewController.swift

@@ -16,6 +16,10 @@ final class RDEPUBReaderHighlightsViewController: UITableViewController {
 
     private let filterControl = UISegmentedControl(items: ["全部", "注释", "划线"])
 
+    /// 空状态提示。放在 tableView 的子视图而不是 `backgroundView`：
+    /// backgroundView 不参与无障碍层级遍历，VoiceOver 与 UI 测试都读不到它。
+    private let emptyStateLabel = UILabel()
+
     private var filteredHighlights: [RDEPUBHighlight] {
         switch filterControl.selectedSegmentIndex {
         case 1:
@@ -120,19 +124,28 @@ final class RDEPUBReaderHighlightsViewController: UITableViewController {
         navigationController?.navigationBar.accessibilityIdentifier = "epub.reader.highlights.navbar"
     }
 
-    private func updateEmptyState() {
-        guard filteredHighlights.isEmpty else {
-            tableView.backgroundView = nil
-            return
-        }
+    private func installEmptyStateLabelIfNeeded() {
+        guard emptyStateLabel.superview == nil else { return }
+        emptyStateLabel.textAlignment = .center
+        emptyStateLabel.numberOfLines = 0
+        emptyStateLabel.translatesAutoresizingMaskIntoConstraints = false
+        emptyStateLabel.accessibilityIdentifier = "epub.reader.highlights.empty"
+        emptyStateLabel.isAccessibilityElement = true
+        tableView.addSubview(emptyStateLabel)
+        // 固定在可视区域居中，不随内容滚动
+        NSLayoutConstraint.activate([
+            emptyStateLabel.centerXAnchor.constraint(equalTo: tableView.frameLayoutGuide.centerXAnchor),
+            emptyStateLabel.centerYAnchor.constraint(equalTo: tableView.frameLayoutGuide.centerYAnchor),
+            emptyStateLabel.leadingAnchor.constraint(greaterThanOrEqualTo: tableView.frameLayoutGuide.leadingAnchor, constant: 24),
+            emptyStateLabel.trailingAnchor.constraint(lessThanOrEqualTo: tableView.frameLayoutGuide.trailingAnchor, constant: -24)
+        ])
+    }
 
-        let label = UILabel()
-        label.text = emptyStateText()
-        label.textAlignment = .center
-        label.textColor = theme.contentTextColor.withAlphaComponent(0.7)
-        label.numberOfLines = 0
-        label.accessibilityIdentifier = "epub.reader.highlights.empty"
-        tableView.backgroundView = label
+    private func updateEmptyState() {
+        installEmptyStateLabelIfNeeded()
+        emptyStateLabel.textColor = theme.contentTextColor.withAlphaComponent(0.7)
+        emptyStateLabel.text = emptyStateText()
+        emptyStateLabel.isHidden = !filteredHighlights.isEmpty
     }
 
     @objc private func filterChangedAction() {
@@ -209,6 +222,9 @@ final class RDEPUBReaderBookmarksViewController: UITableViewController {
         return formatter
     }()
 
+    /// 同 highlights 面板：不能用 `tableView.backgroundView`，那样无障碍读不到。
+    private let emptyStateLabel = UILabel()
+
     init(bookmarks: [RDEPUBBookmark], theme: RDEPUBReaderTheme) {
         self.bookmarks = bookmarks.sorted { $0.createdAt > $1.createdAt }
         self.theme = theme
@@ -279,18 +295,27 @@ final class RDEPUBReaderBookmarksViewController: UITableViewController {
         navigationController?.navigationBar.accessibilityIdentifier = "epub.reader.bookmarks.navbar"
     }
 
+    private func installEmptyStateLabelIfNeeded() {
+        guard emptyStateLabel.superview == nil else { return }
+        emptyStateLabel.text = "暂无书签"
+        emptyStateLabel.textAlignment = .center
+        emptyStateLabel.numberOfLines = 0
+        emptyStateLabel.translatesAutoresizingMaskIntoConstraints = false
+        emptyStateLabel.accessibilityIdentifier = "epub.reader.bookmarks.empty"
+        emptyStateLabel.isAccessibilityElement = true
+        tableView.addSubview(emptyStateLabel)
+        NSLayoutConstraint.activate([
+            emptyStateLabel.centerXAnchor.constraint(equalTo: tableView.frameLayoutGuide.centerXAnchor),
+            emptyStateLabel.centerYAnchor.constraint(equalTo: tableView.frameLayoutGuide.centerYAnchor),
+            emptyStateLabel.leadingAnchor.constraint(greaterThanOrEqualTo: tableView.frameLayoutGuide.leadingAnchor, constant: 24),
+            emptyStateLabel.trailingAnchor.constraint(lessThanOrEqualTo: tableView.frameLayoutGuide.trailingAnchor, constant: -24)
+        ])
+    }
+
     private func updateEmptyState() {
-        guard bookmarks.isEmpty == false else {
-            let label = UILabel()
-            label.text = "暂无书签"
-            label.textAlignment = .center
-            label.textColor = theme.contentTextColor.withAlphaComponent(0.7)
-            label.numberOfLines = 0
-            label.accessibilityIdentifier = "epub.reader.bookmarks.empty"
-            tableView.backgroundView = label
-            return
-        }
-        tableView.backgroundView = nil
+        installEmptyStateLabelIfNeeded()
+        emptyStateLabel.textColor = theme.contentTextColor.withAlphaComponent(0.7)
+        emptyStateLabel.isHidden = !bookmarks.isEmpty
     }
 
     private func titleText(for bookmark: RDEPUBBookmark) -> String {