feat(epub): align wxread css and overlay pagination behavior

Sources/RDReaderView/EPUBTextRendering/RDPlainTextBookBuilder.swift

@@ -13,9 +13,14 @@ import UIKit
 /// 5. CoreText 分页 → RDEPUBTextBook
 public final class RDPlainTextBookBuilder {
     private let renderer: RDEPUBTextRenderer
+    private let layoutConfig: RDEPUBTextLayoutConfig
 
-    public init(renderer: RDEPUBTextRenderer = RDEPUBDTCoreTextRenderer()) {
+    public init(
+        renderer: RDEPUBTextRenderer = RDEPUBDTCoreTextRenderer(),
+        layoutConfig: RDEPUBTextLayoutConfig = .default
+    ) {
         self.renderer = renderer
+        self.layoutConfig = layoutConfig
     }
 
     /// 从纯文本文件构建分页书籍。
@@ -41,7 +46,7 @@ public final class RDPlainTextBookBuilder {
             let rendered = try renderer.renderChapter(html: html, baseURL: nil, style: style)
 
             let content = NSMutableAttributedString(attributedString: rendered.attributedString)
-            let layoutFrames = content.length > 0 ? content.rd_paginatedFrames(size: pageSize) : []
+            let layoutFrames = content.length > 0 ? content.rd_paginatedFrames(size: pageSize, config: layoutConfig) : []
             let effectiveFrames = layoutFrames.isEmpty && content.length > 0
                 ? [
                     RDEPUBTextLayoutFrame(