feat: EPUB阅读器搜索、注释、CFI模块及大书远距跳转优化

- 实现EPUB阅读器搜索功能及选中注释功能
- 优化CFI模块，修复代码审查发现的11个问题
- 实现大书远距目录跳转与后台补全优化方案
- 优化设置面板与章节运行时联动
- 重构及大量改进优化

Sources/RDReaderView/EPUBCore/CFI/RDEPUBCFIRecoveryEngine.swift

@@ -48,7 +48,13 @@ enum RDEPUBCFIRecoveryEngine {
             )
         }
 
-        if let token = tokenRecoveredResult(cfi: cfi, cfiMap: cfiMap, chapterText: chapterText, lastOffset: lastOffset) {
+        if let token = tokenRecoveredResult(
+            cfi: cfi,
+            cfiMap: cfiMap,
+            chapterText: chapterText,
+            fallbackOffset: resolved.chapterOffset,
+            lastOffset: lastOffset
+        ) {
             return token
         }
 
@@ -123,6 +129,7 @@ enum RDEPUBCFIRecoveryEngine {
         cfi: RDEPUBCFI,
         cfiMap: RDEPUBCFIMap?,
         chapterText: String?,
+        fallbackOffset: Int?,
         lastOffset: Int
     ) -> RDEPUBCFIRecoveryResult? {
         guard let cfiMap,
@@ -149,6 +156,7 @@ enum RDEPUBCFIRecoveryEngine {
         let normalizedText = RDEPUBCFITextNodeMapBuilder.normalizedText(from: chapterText)
         guard !normalizedText.isEmpty else { return nil }
 
+        let preferredOffset = fallbackOffset.map { clamp($0, lastOffset: lastOffset) }
         var bestOffset: Int?
         var bestScore = Int.max
 
@@ -161,7 +169,14 @@ enum RDEPUBCFIRecoveryEngine {
                 lastOffset: lastOffset,
                 windowRadius: 768
             )
-            let score = abs(calibrated - approximateOffset)
+            let score = tokenRecoveryScore(
+                for: anchor,
+                targetPath: cfi.contentPath,
+                approximateOffset: approximateOffset,
+                calibratedOffset: calibrated,
+                preferredOffset: preferredOffset,
+                allAnchors: cfiMap.recoveryMetadata.tokenIndex
+            )
             if score < bestScore {
                 bestScore = score
                 bestOffset = calibrated
@@ -317,4 +332,49 @@ enum RDEPUBCFIRecoveryEngine {
     private static func clamp(_ offset: Int, lastOffset: Int) -> Int {
         min(max(offset, 0), max(lastOffset, 0))
     }
+
+    private static func tokenRecoveryScore(
+        for anchor: RDEPUBCFITokenAnchor,
+        targetPath: RDEPUBCFIPath,
+        approximateOffset: Int,
+        calibratedOffset: Int,
+        preferredOffset: Int?,
+        allAnchors: [RDEPUBCFITokenAnchor]
+    ) -> Int {
+        var score = abs(calibratedOffset - approximateOffset)
+        score += pathDistance(anchor.cfiPath, targetPath) * 1_024
+
+        if let preferredOffset {
+            score += abs(approximateOffset - preferredOffset)
+            let expectedOccurrence = nearestOccurrence(
+                forToken: anchor.token,
+                preferredOffset: preferredOffset,
+                anchors: allAnchors
+            )
+            score += abs(anchor.occurrence - expectedOccurrence) * 256
+        }
+
+        return score
+    }
+
+    private static func nearestOccurrence(
+        forToken token: String,
+        preferredOffset: Int,
+        anchors: [RDEPUBCFITokenAnchor]
+    ) -> Int {
+        anchors
+            .filter { $0.token == token }
+            .min(by: { abs($0.chapterOffset - preferredOffset) < abs($1.chapterOffset - preferredOffset) })?
+            .occurrence ?? 0
+    }
+
+    private static func pathDistance(_ lhs: RDEPUBCFIPath, _ rhs: RDEPUBCFIPath) -> Int {
+        let prefix = lhs.commonPrefix(with: rhs).steps.count
+        let remainingLHS = lhs.steps.dropFirst(prefix)
+        let remainingRHS = rhs.steps.dropFirst(prefix)
+        let stepDistance = zip(remainingLHS, remainingRHS).reduce(0) { partial, pair in
+            partial + abs(pair.0.index - pair.1.index)
+        }
+        return stepDistance + abs(lhs.steps.count - rhs.steps.count) * 2
+    }
 }