安全区域改为从 key window 动态获取

- 新增 RDEPUBSafeArea：参考 GKNavigationBarSwift 的 keyWindow 三级查找与临时 window 兜底
- 移除 reflowableContentInsets 中 top/bottom 40 的固定默认值，改按设备真实安全区生成
- 各取安全区处的 ?? .zero 兜底改为回退到 key window 值
- DEBUG 构建下为文本可读区域绘制红色边框，方便查看排版范围

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Sources/RDReaderView/EPUBUI/RDURLReaderController.swift

@@ -154,7 +154,7 @@ public final class RDURLReaderController: UIViewController {
             let bookTitle = bookURL.deletingPathExtension().lastPathComponent
             let pageSize = currentTextPageSize()
             let renderStyle = currentTextRenderStyle()
-            let safeInsets = view.safeAreaInsets
+            let safeInsets = RDEPUBSafeArea.resolve(view.safeAreaInsets)
             let edgeInsets = UIEdgeInsets(
                 top: max(epubConfiguration.reflowableContentInsets.top, safeInsets.top),
                 left: max(epubConfiguration.reflowableContentInsets.left, safeInsets.left),

Sources/RDReaderView/EPUBUI/ReaderController/RDEPUBReaderContext.swift

@@ -163,7 +163,7 @@ final class RDEPUBReaderContext {
     }
 
     func currentPreferences() -> RDEPUBPreferences {
-        let safeInsets = controller?.view.safeAreaInsets ?? .zero
+        let safeInsets = RDEPUBSafeArea.resolve(controller?.view.safeAreaInsets)
         return configuration.makePreferences(safeAreaInsets: safeInsets)
     }
 

Sources/RDReaderView/EPUBUI/ReaderController/RDEPUBReaderEnvironment.swift

@@ -47,7 +47,7 @@ final class RDEPUBReaderEnvironment {
         return RDEPUBNavigatorLayoutContext(
             containerSize: resolvedSize,
             pagesPerScreen: readerView?.pagesPerScreen ?? 1,
-            safeAreaInsets: controller?.view.safeAreaInsets ?? .zero,
+            safeAreaInsets: RDEPUBSafeArea.resolve(controller?.view.safeAreaInsets),
             userInterfaceIdiom: controller?.traitCollection.userInterfaceIdiom ?? .phone,
             reflowableContentInsets: configuration.reflowableContentInsets
         )
@@ -68,7 +68,7 @@ final class RDEPUBReaderEnvironment {
         configuration: RDEPUBReaderConfiguration,
         pageSize: CGSize
     ) -> RDEPUBTextLayoutConfig {
-        let safeAreaInsets = controller?.view.safeAreaInsets ?? .zero
+        let safeAreaInsets = RDEPUBSafeArea.resolve(controller?.view.safeAreaInsets)
         return RDEPUBTextLayoutConfig(
             frameWidth: max(pageSize.width, 1),
             frameHeight: max(pageSize.height, 1),

Sources/RDReaderView/EPUBUI/Settings/RDEPUBReaderConfiguration.swift

@@ -109,7 +109,7 @@ public struct RDEPUBReaderConfiguration: Equatable {
         showsTableOfContents: Bool = true,
         allowsHighlights: Bool = true,
         showsSettingsPanel: Bool = true,
-        reflowableContentInsets: UIEdgeInsets = UIEdgeInsets(top: 40, left: 16, bottom: 40, right: 16),
+        reflowableContentInsets: UIEdgeInsets = RDEPUBSafeArea.defaultReflowableContentInsets(),
         fixedContentInset: UIEdgeInsets = .zero,
         theme: RDEPUBReaderTheme = .light,
         darkImageAdjustmentEnabled: Bool = true,
@@ -172,11 +172,13 @@ extension RDEPUBReaderConfiguration {
     func makePreferences(safeAreaInsets: UIEdgeInsets = .zero) -> RDEPUBPreferences {
         // Use the larger of reflowableContentInsets and safeAreaInsets for each edge
         // to prevent content from being hidden under Dynamic Island / home indicator.
+        // Falls back to the key-window safe area when the caller has no laid-out view.
+        let resolvedSafeAreaInsets = RDEPUBSafeArea.resolve(safeAreaInsets)
         let safeInsets = UIEdgeInsets(
-            top: max(reflowableContentInsets.top, safeAreaInsets.top),
-            left: max(reflowableContentInsets.left, safeAreaInsets.left),
-            bottom: max(reflowableContentInsets.bottom, safeAreaInsets.bottom),
-            right: max(reflowableContentInsets.right, safeAreaInsets.right)
+            top: max(reflowableContentInsets.top, resolvedSafeAreaInsets.top),
+            left: max(reflowableContentInsets.left, resolvedSafeAreaInsets.left),
+            bottom: max(reflowableContentInsets.bottom, resolvedSafeAreaInsets.bottom),
+            right: max(reflowableContentInsets.right, resolvedSafeAreaInsets.right)
         )
         return RDEPUBPreferences(
             fontSize: fontSize,

Sources/RDReaderView/EPUBUI/TextPage/RDEPUBTextContentView.swift

@@ -126,6 +126,19 @@ final class RDEPUBTextContentView: UIView, UIGestureRecognizerDelegate, RDReader
         return spinner
     }()
 
+#if DEBUG
+    /// Debug-only outline of the readable content area (bounds inset by contentInsets).
+    private let debugContentAreaBorderView: UIView = {
+        let view = UIView()
+        view.isUserInteractionEnabled = false
+        view.backgroundColor = .clear
+        view.layer.borderColor = UIColor.systemRed.withAlphaComponent(0.6).cgColor
+        view.layer.borderWidth = 1
+        view.accessibilityIdentifier = "epub.reader.debug.contentAreaBorder"
+        return view
+    }()
+#endif
+
     private lazy var longPressGestureRecognizer: UILongPressGestureRecognizer = {
         let gesture = UILongPressGestureRecognizer(target: self, action: #selector(handleLongPress(_:)))
         gesture.minimumPressDuration = 0.5
@@ -243,6 +256,9 @@ final class RDEPUBTextContentView: UIView, UIGestureRecognizerDelegate, RDReader
         addSubview(pageNumberLabel)
         addSubview(loadingSpinner)
         addSubview(selectionLoupeView)
+#if DEBUG
+        addSubview(debugContentAreaBorderView)
+#endif
         addGestureRecognizer(longPressGestureRecognizer)
         addGestureRecognizer(panGestureRecognizer)
         addGestureRecognizer(tapGestureRecognizer)
@@ -338,6 +354,9 @@ final class RDEPUBTextContentView: UIView, UIGestureRecognizerDelegate, RDReader
         coverImageView.frame = bounds.inset(by: contentInsets)
 
         let contentRect = bounds.inset(by: contentInsets)
+#if DEBUG
+        debugContentAreaBorderView.frame = contentRect
+#endif
         let labelSize = pageNumberLabel.sizeThatFits(
             CGSize(width: contentRect.width, height: Self.pageNumberReservedHeight)
         )
@@ -374,7 +393,7 @@ final class RDEPUBTextContentView: UIView, UIGestureRecognizerDelegate, RDReader
         selectionController.clearSelection(renderView: coreTextRenderView)
         contentInsets = Self.safeContentInsets(
             configuration: configuration,
-            safeAreaInsets: safeAreaInsets
+            safeAreaInsets: RDEPUBSafeArea.resolve(safeAreaInsets)
         )
         backgroundColor = configuration.theme.contentBackgroundColor
         pageNumberLabel.textColor = configuration.theme.contentTextColor
@@ -459,7 +478,7 @@ final class RDEPUBTextContentView: UIView, UIGestureRecognizerDelegate, RDReader
         selectionController.clearSelection(renderView: coreTextRenderView)
         contentInsets = Self.safeContentInsets(
             configuration: configuration,
-            safeAreaInsets: safeAreaInsets
+            safeAreaInsets: RDEPUBSafeArea.resolve(safeAreaInsets)
         )
         backgroundColor = configuration.theme.contentBackgroundColor
         pageNumberLabel.textColor = configuration.theme.contentTextColor