refactor: split reader architecture and chrome handling

Sources/RDReaderView/EPUBTextRendering/RDEPUBTextRenderer.swift

@@ -100,6 +100,8 @@ public struct RDEPUBTextLayoutConfig: Equatable {
     public var hyphenation: Bool
     /// 图片最大高度占页面高度的比例
     public var imageMaxHeightRatio: CGFloat
+    /// 当调用方暂时拿不到 pageSize 时，用于估算附件尺寸的兜底 viewport。
+    public var fallbackViewportSize: CGSize
 
     public init(
         frameWidth: CGFloat = 0,
@@ -111,7 +113,8 @@ public struct RDEPUBTextLayoutConfig: Equatable {
         avoidWidows: Bool = true,
         avoidPageBreakInsideEnabled: Bool = true,
         hyphenation: Bool = true,
-        imageMaxHeightRatio: CGFloat = 0.85
+        imageMaxHeightRatio: CGFloat = 0.85,
+        fallbackViewportSize: CGSize = CGSize(width: 375, height: 667)
     ) {
         self.frameWidth = frameWidth
         self.frameHeight = frameHeight
@@ -123,6 +126,7 @@ public struct RDEPUBTextLayoutConfig: Equatable {
         self.avoidPageBreakInsideEnabled = avoidPageBreakInsideEnabled
         self.hyphenation = hyphenation
         self.imageMaxHeightRatio = imageMaxHeightRatio
+        self.fallbackViewportSize = fallbackViewportSize
     }
 
     /// 默认配置
@@ -172,7 +176,9 @@ public struct RDEPUBTextLayoutConfig: Equatable {
             avoidWidows ? "1" : "0",
             avoidPageBreakInsideEnabled ? "1" : "0",
             hyphenation ? "1" : "0",
-            String(format: "%.3f", imageMaxHeightRatio)
+            String(format: "%.3f", imageMaxHeightRatio),
+            String(format: "%.3f", fallbackViewportSize.width),
+            String(format: "%.3f", fallbackViewportSize.height)
         ].joined(separator: "|")
     }
 }