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

Sources/RDReaderView/EPUBTextRendering/RDEPUBTextLayouter.swift

@@ -27,6 +27,8 @@ struct RDEPUBTextLayouter {
     private let framesetter: CTFramesetter
     /// 页面矩形路径（用于 CTFrame 排版）
     private let path: CGPath
+    /// DTCoreText 路径可直接消费的单矩形布局区域
+    private let dtLayoutRect: CGRect
     /// 布局配置（avoidPageBreakInside、孤行控制等）
     private let config: RDEPUBTextLayoutConfig
 
@@ -35,7 +37,8 @@ struct RDEPUBTextLayouter {
         self.pageSize = pageSize
         self.config = config
         self.framesetter = CTFramesetterCreateWithAttributedString(attributedString)
-        self.path = CGPath(rect: CGRect(origin: .zero, size: pageSize), transform: nil)
+        self.dtLayoutRect = config.contentRect(fallback: pageSize)
+        self.path = Self.makeLayoutPath(pageSize: pageSize, config: config)
     }
 
     /// 执行分页，返回布局帧列表（每帧对应一页）。
@@ -119,6 +122,10 @@ struct RDEPUBTextLayouter {
 #if canImport(DTCoreText)
     /// 使用 DTCoreTextLayouter 进行分页，提供更精确的行级语义处理。
     private func layoutFramesUsingDTCoreText(fragmentOffsets: [String: Int]) -> [RDEPUBTextLayoutFrame] {
+        guard config.numberOfColumns == 1 else {
+            return layoutFramesUsingCoreText(fragmentOffsets: fragmentOffsets)
+        }
+
         guard let layouter = DTCoreTextLayouter(attributedString: attributedString) else {
             return layoutFramesUsingCoreText(fragmentOffsets: fragmentOffsets)
         }
@@ -127,7 +134,7 @@ struct RDEPUBTextLayouter {
 
         var frames: [RDEPUBTextLayoutFrame] = []
         var location = 0
-        let pageRect = CGRect(origin: .zero, size: pageSize)
+        let pageRect = dtLayoutRect
 
         while location < attributedString.length {
             guard let layoutFrame = layouter.layoutFrame(with: pageRect, range: NSRange(location: location, length: 0)) else {
@@ -180,6 +187,19 @@ struct RDEPUBTextLayouter {
     }
 #endif
 
+    private static func makeLayoutPath(pageSize: CGSize, config: RDEPUBTextLayoutConfig) -> CGPath {
+        let columnRects = config.columnRects(fallback: pageSize)
+        guard columnRects.count > 1 else {
+            return CGPath(rect: columnRects.first ?? CGRect(origin: .zero, size: pageSize), transform: nil)
+        }
+
+        let path = CGMutablePath()
+        for rect in columnRects {
+            path.addRect(rect)
+        }
+        return path
+    }
+
     // MARK: - 语义边界调整
 
     /// 对 CoreText 提出的分页范围进行语义边界调整。