fix: pageCurl翻页后偶尔刷新回章节第一页

根因：.extendPartial pageMap更新提交时使用了异步扩展开始时捕获的
currentPageNumber/currentLocation，在pageCurl模式下用户可能已经翻了几页，
导致过时值通过transitionToPage把用户拉回旧位置。

修复三点：
1. PresentationRuntime: .extendPartial fallback不再使用捕获的
   currentPageNumber，改用readerView.currentPage实时值
2. ChapterWarmupOrchestrator: 异步加载完成回调中使用实时位置
   (readerView.currentPage + locationCoordinator.currentVisibleLocation())
   而非异步开始时捕获的旧值
3. PresentationRuntime: rebindVisiblePage在pageCurl模式下，
   如果正在翻页动画中(isPageCurlTransitioning)，延迟到动画结束后
   再用实时currentPage执行transitionToPage，避免在pageNum回调栈
   内同步触发transitionToPage导致重入

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

Sources/RDReaderView/EPUBUI/ReaderController/ChapterRuntime/RDEPUBChapterWarmupOrchestrator.swift

@@ -183,9 +183,13 @@ final class RDEPUBChapterWarmupOrchestrator {
         group.notify(queue: .main) { [weak self] in
             guard let self else { return }
             defer { self.endPartialBookPageMapExtension() }
+            // Use live position values rather than the stale captured values,
+            // since the user may have turned several pages since the extension began.
+            let livePageNumber = max(self.context.readerView?.currentPage ?? 0, 0) + 1
+            let liveLocation = self.locationCoordinator.currentVisibleLocation()
             self.applyAsyncPartialBookPageMapExtension(
-                currentPageNumber: currentPageNumber,
-                currentLocation: currentLocation,
+                currentPageNumber: livePageNumber,
+                currentLocation: liveLocation,
                 currentMap: currentMap,
                 loadedChapters: loadedChapters
             )