Reorganize docs and update reader search flows

Sources/RDReaderView/EPUBUI/RDEPUBReaderController+ContentDelegates.swift

@@ -202,7 +202,6 @@ extension RDEPUBReaderController: RDEPUBTextContentViewDelegate {
         }
 
         guard let textBook,
-              let publication,
               let page = textBook.page(at: pageNumber) else {
             return nil
         }
@@ -211,11 +210,14 @@ extension RDEPUBReaderController: RDEPUBTextContentViewDelegate {
             ?? textBook.location(forPageNumber: pageNumber, bookIdentifier: currentBookIdentifier)
         guard let location else { return nil }
 
-        return publication.resourceResolver.normalizedLocation(
-            location,
-            relativeToSpineIndex: nil,
-            bookIdentifier: currentBookIdentifier
-        ) ?? location
+        if let publication {
+            return publication.resourceResolver.normalizedLocation(
+                location,
+                relativeToSpineIndex: nil,
+                bookIdentifier: currentBookIdentifier
+            ) ?? location
+        }
+        return location
     }
 
     /// 同步文本阅读状态到阅读会话（页码、位置、spine、章节等）