feat: chapter runtime refactoring and related updates

- Refactor chapter runtime: replace window coordinator/snapshot with warmup orchestrator
- Update EPUB core: parser, reading session, JS bridge, navigator layout
- Update reader controller: data source, location resolution, persistence
- Update chapter runtime: data cache, loader, runtime store, disk cache, warmup orchestrator
- Remove deprecated navigation state machine and pagination state
- Update text rendering: book cache, HTML normalizer
- Update UI: text content view, dark image adjuster, text selection controller
- Update settings and reader configuration
- Add CODE_REVIEW.md and AUDIT_FINAL.md documentation
- Update pod dependencies (remove SSAlertSwift, SnapKit)
- Update podspec and pod configuration files

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

Sources/RDReaderView/EPUBUI/ReaderController/RDEPUBReaderContext.swift

@@ -1,5 +1,14 @@
 import UIKit
 
+/// Captures layout parameters on the main thread for safe use on background queues.
+/// Create via `RDEPUBReaderContext.makeLayoutSnapshot()` before dispatching work off the main thread.
+struct RDEPUBLayoutSnapshot {
+    let pageSize: CGSize
+    let style: RDEPUBTextRenderStyle
+    let layoutConfig: RDEPUBTextLayoutConfig
+    let renderSignature: String
+}
+
 final class RDEPUBReaderContext {
 
     private let activityLock = NSLock()
@@ -73,11 +82,6 @@ final class RDEPUBReaderContext {
         set { state.paginationToken = newValue }
     }
 
-    var paginator: RDEPUBPaginator? {
-        get { state.paginator }
-        set { state.paginator = newValue }
-    }
-
     var searchState: RDEPUBSearchState? {
         get { state.searchState }
         set { state.searchState = newValue }
@@ -159,43 +163,57 @@ final class RDEPUBReaderContext {
     }
 
     func currentPreferences() -> RDEPUBPreferences {
-        configuration.makePreferences()
+        let safeInsets = controller?.view.safeAreaInsets ?? .zero
+        return configuration.makePreferences(safeAreaInsets: safeInsets)
+    }
+
+    /// Captures all layout parameters needed for background chapter loading.
+    /// Must be called on the main thread. The returned snapshot is safe to use on any thread.
+    func makeLayoutSnapshot() -> RDEPUBLayoutSnapshot {
+        dispatchPrecondition(condition: .onQueue(.main))
+        let pageSize = currentTextPageSize()
+        let style = currentTextRenderStyle()
+        let layoutConfig = currentTextLayoutConfig(pageSize: pageSize)
+        let renderSignature = renderSignature(style: style, pageSize: pageSize, layoutConfig: layoutConfig)
+        return RDEPUBLayoutSnapshot(
+            pageSize: pageSize,
+            style: style,
+            layoutConfig: layoutConfig,
+            renderSignature: renderSignature
+        )
     }
 
     func currentTextPageSize() -> CGSize {
-        if Thread.isMainThread {
-            let pageNum = (readerView?.currentPage ?? -1) >= 0 ? readerView?.currentPage : nil
-            if let readerView, let pageNum {
-                let resolvedSize = readerView.resolvedSinglePageSize(pageNum: pageNum)
-                if resolvedSize.width > 0, resolvedSize.height > 0 {
-                    return resolvedSize
-                }
+        // M-04: Use dispatchPrecondition instead of assert so it's enforced in Release builds too.
+        dispatchPrecondition(condition: .onQueue(.main))
+
+        let pageNum = (readerView?.currentPage ?? -1) >= 0 ? readerView?.currentPage : nil
+        if let readerView, let pageNum {
+            let resolvedSize = readerView.resolvedSinglePageSize(pageNum: pageNum)
+            if resolvedSize.width > 0, resolvedSize.height > 0 {
+                return resolvedSize
             }
-            let viewportSize = currentLayoutContext().viewportSize
-            if viewportSize.width > 0, viewportSize.height > 0 {
-                return viewportSize
-            }
-        } else if let lastTextPaginationPageSize,
-                  lastTextPaginationPageSize.width > 0,
-                  lastTextPaginationPageSize.height > 0 {
+        }
+        let viewportSize = currentLayoutContext().viewportSize
+        if viewportSize.width > 0, viewportSize.height > 0 {
+            return viewportSize
+        }
+        if let lastTextPaginationPageSize,
+           lastTextPaginationPageSize.width > 0,
+           lastTextPaginationPageSize.height > 0 {
             return lastTextPaginationPageSize
-        } else {
-            let mainThreadSize = DispatchQueue.main.sync { [weak self] in
-                self?.currentTextPageSize() ?? .zero
-            }
-            if mainThreadSize.width > 0, mainThreadSize.height > 0 {
-                return mainThreadSize
-            }
         }
         return environment.fallbackViewportSize
     }
 
     func currentTextRenderStyle() -> RDEPUBTextRenderStyle {
-        environment.currentTextRenderStyle(configuration: configuration)
+        dispatchPrecondition(condition: .onQueue(.main))
+        return environment.currentTextRenderStyle(configuration: configuration)
     }
 
     func currentTextLayoutConfig(pageSize: CGSize) -> RDEPUBTextLayoutConfig {
-        environment.currentTextLayoutConfig(configuration: configuration, pageSize: pageSize)
+        dispatchPrecondition(condition: .onQueue(.main))
+        return environment.currentTextLayoutConfig(configuration: configuration, pageSize: pageSize)
     }
 
     func resolvedTextRenderer() -> RDEPUBTextRenderer {
@@ -282,10 +300,19 @@ final class RDEPUBReaderContext {
     }
 
     func currentRenderSignature() -> String {
+        dispatchPrecondition(condition: .onQueue(.main))
         let style = currentTextRenderStyle()
         let pageSize = currentTextPageSize()
         let layoutConfig = currentTextLayoutConfig(pageSize: pageSize)
-        return [
+        return renderSignature(style: style, pageSize: pageSize, layoutConfig: layoutConfig)
+    }
+
+    private func renderSignature(
+        style: RDEPUBTextRenderStyle,
+        pageSize: CGSize,
+        layoutConfig: RDEPUBTextLayoutConfig
+    ) -> String {
+        [
             style.font.fontName,
             "\(style.font.pointSize)",
             "\(configuration.lineHeightMultiple)",