完善搜索定位与内存监测回归验证

本次提交围绕搜索链路的稳定性、定位恢复体验以及长章节内存优化的验证能力进行了补强。

主要改动：

1. 调整阅读器搜索栏、搜索协调器与定位恢复逻辑，改善搜索结果跳转、状态同步与相关 UI 行为。

2. 补充内存探针接入点与上下文记录，便于跟踪阅读过程中的内存占用变化。

3. 更新 RDURLReaderController、ReaderContext 与工具视图相关实现，使调试与观测链路更完整。

4. 新增 MemoryFootprintTests，并同步更新 DemoReaderState 与 SearchTests，用 UI 测试覆盖搜索与内存相关回归场景。

Sources/RDReaderView/EPUBUI/ReaderController/RDEPUBMemoryProbe.swift

@@ -22,8 +22,13 @@ enum RDEPUBMemoryProbe {
 
     static func log(_ event: String) {
         guard isEnabled else { return }
-        let megabytes = Double(currentFootprint()) / 1_048_576
-        print(String(format: "[EPUB][MemoryProbe] %@ footprint=%.1fMB", event, megabytes))
+        print(String(format: "[EPUB][MemoryProbe] %@ footprint=%.1fMB", event, footprintMB))
+    }
+
+    /// Current phys_footprint in MB. Cheap enough (one task_info call) to
+    /// surface in the demo state snapshot for automated memory assertions.
+    static var footprintMB: Double {
+        Double(currentFootprint()) / 1_048_576
     }
 
     /// phys_footprint matches the value Xcode's memory gauge and Jetsam use.

Sources/RDReaderView/EPUBUI/ReaderController/RDEPUBReaderContext.swift

@@ -377,10 +377,12 @@ final class RDEPUBReaderContext {
     }
 
     func textChapterData(forNormalizedHref href: String) -> RDEPUBChapterData? {
-        guard let textBook, let publication else { return nil }
-        let normalizedHref = publication.resourceResolver.normalizedHref(href) ?? href
+        guard let textBook else { return nil }
+        // External text books (e.g. plain .txt) have no publication; their
+        // chapter hrefs are matched verbatim.
+        let normalizedHref = publication?.resourceResolver.normalizedHref(href) ?? href
         return textBook.chapters.lazy
-            .first(where: { (publication.resourceResolver.normalizedHref($0.href) ?? $0.href) == normalizedHref })
+            .first(where: { (publication?.resourceResolver.normalizedHref($0.href) ?? $0.href) == normalizedHref })
             .flatMap { textBook.chapterData(for: $0.href) }
     }
 

Sources/RDReaderView/EPUBUI/ReaderController/RDEPUBReaderSearchCoordinator.swift

@@ -143,6 +143,12 @@ final class RDEPUBReaderSearchCoordinator {
         if let textBook = controller.textBook, let publication = controller.publication {
             return .textBook(textBook, publication)
         }
+        // External text books (e.g. plain .txt) carry a textBook but no
+        // publication/parser/bookPageMap; search over the chapter text
+        // directly using hrefs from the textBook itself.
+        if let textBook = controller.textBook {
+            return .externalTextBook(textBook)
+        }
         if controller.readerContext.bookPageMap != nil, let publication = controller.publication {
             return .onDemand(publication)
         }
@@ -157,6 +163,8 @@ final class RDEPUBReaderSearchCoordinator {
         switch engine {
         case .textBook(let textBook, let publication):
             return RDEPUBTextSearchEngine(textBook: textBook, publication: publication).search(keyword: keyword)
+        case .externalTextBook(let textBook):
+            return RDEPUBTextSearchEngine.searchWithoutPublication(textBook: textBook, keyword: keyword)
         case .onDemand(let publication):
             return resolvedOnDemandSearchMatches(for: keyword, publication: publication, layoutSnapshot: layoutSnapshot)
         case .html(let parser, let publication):
@@ -166,6 +174,7 @@ final class RDEPUBReaderSearchCoordinator {
 
     private enum SearchEngineSnapshot {
         case textBook(RDEPUBTextBook, RDEPUBPublication)
+        case externalTextBook(RDEPUBTextBook)
         case onDemand(RDEPUBPublication)
         case html(RDEPUBParser, RDEPUBPublication)
     }
@@ -350,12 +359,16 @@ final class RDEPUBReaderSearchCoordinator {
             rangeCFI: searchMatch.rangeCFI
         )
 
-        if let textBook = controller.textBook, let publication = controller.publication {
-            return textBook.pageNumber(
-                for: location,
-                resolver: publication.resourceResolver,
-                bookIdentifier: controller.currentBookIdentifier
-            )
+        if let textBook = controller.textBook {
+            if let publication = controller.publication {
+                return textBook.pageNumber(
+                    for: location,
+                    resolver: publication.resourceResolver,
+                    bookIdentifier: controller.currentBookIdentifier
+                )
+            }
+            // External text books have no resolver; hrefs match verbatim.
+            return textBook.chapterData(for: location.href)?.pageNumber(for: location)
         }
 
         return controller.readingSession?.pageIndex(