feat: 实现大书远距目录跳转与后台补全优化方案

Phase 1: 稳定性优先
- 新增 RDEPUBJumpSession 保护机制，防止远距跳转后翻页串章
- 升级页图接管条件，增加 JumpSession 保护区检查
- 窗口扩展改为基于当前权威窗口方向

Phase 2: 补全优先级重排
- 新增 RDEPUBBackgroundPriorityPolicy 策略配置
- 实现 hot/warm/cold zone 优先级排序
- 添加失败重试机制（指数退避，最多3次）

Phase 3: 分段覆盖与最终收敛
- 新增 RDEPUBBackgroundCoverageStore 分段存储
- 新增 RDEPUBPageMapReconciliationCoordinator 页图接管仲裁
- 实现 LRU 淘汰和内存警告处理

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Sources/RDReaderView/EPUBUI/RDEPUBReaderController+DataSource.swift

@@ -296,31 +296,41 @@ extension RDEPUBReaderController: RDReaderDataSource, RDReaderDelegate {
         reconcileTextPaginationSizeIfNeeded(for: pageNum)
 
         // 用户开始导航时，应用后台解析完成的完整 map
+        let previousCurrentPage = readerView.currentPage
         runtime.applyPendingFullPageMapIfNeeded()
+        let effectivePageNum = readerView.currentPage >= 0 ? readerView.currentPage : pageNum
+        if previousCurrentPage != readerView.currentPage, effectivePageNum != pageNum {
+            return
+        }
 
         if readerContext.bookPageMap != nil {
-            _ = runtime.prepareOnDemandChapter(forAbsolutePageNumber: pageNum + 1)
-            runtime.extendPartialBookPageMapIfNeeded(currentPageNumber: pageNum + 1)
+            _ = runtime.prepareOnDemandChapter(forAbsolutePageNumber: effectivePageNum + 1)
+            runtime.extendPartialBookPageMapIfNeeded(currentPageNumber: effectivePageNum + 1)
         }
 
         let totalPages = pageCountOfReaderView(readerView: readerView)
-        if totalPages > 0, pageNum == totalPages - 1 {
+        if totalPages > 0, effectivePageNum == totalPages - 1 {
             delegate?.epubReaderDidReachEnd(self)
         }
 
         if (textBook != nil || readerContext.bookPageMap != nil),
-           let location = resolvedTextLocation(forPageNumber: pageNum + 1) {
+           let location = resolvedTextLocation(forPageNumber: effectivePageNum + 1) {
             persist(location: location)
-            synchronizeTextReadingState(pageNumber: pageNum + 1, location: location)
+            synchronizeTextReadingState(pageNumber: effectivePageNum + 1, location: location)
+            // 记录翻页到 JumpSession
+            runtime.locationCoordinator.recordPageChangeIfNeeded()
             return
         }
 
-        if let location = fallbackLocation(for: pageNum) {
+        if let location = fallbackLocation(for: effectivePageNum) {
             persist(location: location)
         }
         if readingSession?.navigatorState == .jumping || readingSession?.navigatorState == .moving {
             readingSession?.transition(to: .idle)
         }
+
+        // 记录翻页到 JumpSession
+        runtime.locationCoordinator.recordPageChangeIfNeeded()
     }
 
     /// 屏幕方向即将变化回调，捕获待恢复的展示位置