feat(reader): 实现大书快速进入与增量分页路径

- PaginationCoordinator: 新增 textReflowable 快速进入路径，支持增量章节构建
  与 staged 合并策略，避免整书一次性构建的主线程阻塞
- TextBookBuilder: 重构为支持单章构建与增量合并模式
- ChapterPageCounter: 优化分页计数逻辑，支持章节级分页缓存
- PageFrameFactory: 新增 CoreText 页面帧工厂，提升排版性能
- ReaderContext/ReaderRuntime: 适配增量分页状态管理

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

Sources/RDReaderView/EPUBTextRendering/RDEPUBDTCoreTextRenderer.swift

@@ -41,7 +41,11 @@ public struct RDEPUBDTCoreTextRenderer: RDEPUBTextRenderer {
         let attributedString = NSMutableAttributedString(attributedString: rendered)
         RDEPUBSemanticMarkerInjector.applyPaginationSemantics(in: attributedString)
         let fragmentOffsets = RDEPUBFragmentMarkerInjector.extractFragmentOffsets(from: attributedString)
-        RDEPUBTextRendererSupport.normalizeReadingAttributes(in: attributedString, style: request.style)
+        RDEPUBTextRendererSupport.normalizeReadingAttributes(
+            in: attributedString,
+            style: request.style,
+            layoutConfig: request.layoutConfig ?? .default
+        )
         return RDEPUBRenderedChapterContent(
             attributedString: attributedString,
             fragmentOffsets: fragmentOffsets,
@@ -76,7 +80,11 @@ public struct RDEPUBDTCoreTextRenderer: RDEPUBTextRenderer {
         let attributedString = RDEPUBTextRendererSupport.fallbackAttributedString(for: request.context.html, style: request.style)
         RDEPUBSemanticMarkerInjector.applyPaginationSemantics(in: attributedString)
         let fragmentOffsets = RDEPUBFragmentMarkerInjector.extractFragmentOffsets(from: attributedString)
-        RDEPUBTextRendererSupport.normalizeReadingAttributes(in: attributedString, style: request.style)
+        RDEPUBTextRendererSupport.normalizeReadingAttributes(
+            in: attributedString,
+            style: request.style,
+            layoutConfig: request.layoutConfig ?? .default
+        )
         return RDEPUBRenderedChapterContent(
             attributedString: attributedString,
             fragmentOffsets: fragmentOffsets,