feat: 设置面板与章节运行时联动优化

- 设置页打开时仅重新计算当前章节预览，关闭后触发完整补全
- 新增 preview 加载优先级，支持设置页内当前章预览
- 添加设置页防抖机制，合并连续字号/行距变更
- 支持下滑手势关闭设置页，通过 presentation delegate 通知运行时
- 重新分页时跳过导航和尺寸校验，避免状态冲突
- currentTextPageSize 线程安全优化，后台线程使用缓存尺寸
- 更新 CocoaPods 依赖

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

Sources/RDReaderView/EPUBUI/ReaderController/RDEPUBReaderContext.swift

@@ -122,14 +122,31 @@ final class RDEPUBReaderContext {
 
     /// 获取当前文本排版的单页尺寸，优先从 readerView 解析，兜底用布局上下文。
     func currentTextPageSize() -> CGSize {
-        let pageNum = (readerView?.currentPage ?? -1) >= 0 ? readerView?.currentPage : nil
-        if let readerView, let pageNum {
-            let resolvedSize = readerView.resolvedSinglePageSize(pageNum: pageNum)
-            if resolvedSize.width > 0, resolvedSize.height > 0 {
-                return resolvedSize
+        if Thread.isMainThread {
+            let pageNum = (readerView?.currentPage ?? -1) >= 0 ? readerView?.currentPage : nil
+            if let readerView, let pageNum {
+                let resolvedSize = readerView.resolvedSinglePageSize(pageNum: pageNum)
+                if resolvedSize.width > 0, resolvedSize.height > 0 {
+                    return resolvedSize
+                }
+            }
+            let viewportSize = currentLayoutContext().viewportSize
+            if viewportSize.width > 0, viewportSize.height > 0 {
+                return viewportSize
+            }
+        } else if let lastTextPaginationPageSize,
+                  lastTextPaginationPageSize.width > 0,
+                  lastTextPaginationPageSize.height > 0 {
+            return lastTextPaginationPageSize
+        } else {
+            let mainThreadSize = DispatchQueue.main.sync { [weak self] in
+                self?.currentTextPageSize() ?? .zero
+            }
+            if mainThreadSize.width > 0, mainThreadSize.height > 0 {
+                return mainThreadSize
             }
         }
-        return currentLayoutContext().viewportSize
+        return dependencies.environment.fallbackViewportSize
     }
 
     /// 根据当前配置生成文本渲染样式（字体、行距、颜色）。