全量换表前用旧页表回环验证当前位置

初始 partial 窗口被全书页表接管时,live 页码(窗口坐标)与新表解析
页码(全书坐标)不可比,±1 启发式误判后 preserveLivePage 会把模型
位置钉在全书第 1 页,导致位置错乱并级联阻塞后续全表提交。改为换表
前先用旧表解析 currentLocation:回环等于 live 页说明位置忠实反映
屏幕内容,换表后无条件信任新表解析结果;不等时才退回 ±1 门槛,保留
对 stale 持久化位置的防护。

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

Sources/RDReaderView/EPUBUI/ReaderController/RDEPUBPresentationRuntime.swift

@@ -160,6 +160,11 @@ final class RDEPUBPresentationRuntime {
     ) {
         let currentLocation = locationCoordinator.currentVisibleLocation()
         let livePageBeforeApply = readerView.currentPage + 1
+        // Resolved against the outgoing page map. When it round-trips to the live
+        // page, the location faithfully describes what is on screen, so whatever
+        // page it resolves to in the new map is authoritative even if the two maps
+        // number pages differently (partial-window -> full-book takeover).
+        let oldResolvedPage = currentLocation.flatMap { controller.pageNumber(for: $0) }
 
         context.textBook = nil
         applyPageMapToLiveModel(newPageMap)
@@ -172,11 +177,12 @@ final class RDEPUBPresentationRuntime {
             let resolvedTargetPage = controller.pageNumber(for: currentLocation)
             let shouldTrustResolvedLocation = shouldTrustFullReplaceResolvedPage(
                 resolvedTargetPage,
-                livePageBeforeApply: livePageBeforeApply
+                livePageBeforeApply: livePageBeforeApply,
+                locationMatchesLivePage: oldResolvedPage == livePageBeforeApply
             )
             RDEPUBBackgroundTrace.log(
                 "Reconciliation",
-                "applyFullPageMapReplacement decision livePage=\(livePageBeforeApply) resolvedTargetPage=\(resolvedTargetPage ?? -1) trustResolved=\(shouldTrustResolvedLocation) href=\(currentLocation.href)"
+                "applyFullPageMapReplacement decision livePage=\(livePageBeforeApply) oldResolvedPage=\(oldResolvedPage ?? -1) resolvedTargetPage=\(resolvedTargetPage ?? -1) trustResolved=\(shouldTrustResolvedLocation) href=\(currentLocation.href)"
             )
 
             if shouldTrustResolvedLocation,
@@ -433,9 +439,16 @@ final class RDEPUBPresentationRuntime {
 
     private func shouldTrustFullReplaceResolvedPage(
         _ resolvedTargetPage: Int?,
-        livePageBeforeApply: Int
+        livePageBeforeApply: Int,
+        locationMatchesLivePage: Bool
     ) -> Bool {
         guard let resolvedTargetPage else { return false }
+        if locationMatchesLivePage {
+            return true
+        }
+        // The location did not round-trip to the live page in the outgoing map
+        // (stale persisted location or mid-transition), so only follow it when it
+        // stays next to the page the user is actually looking at.
         return abs(resolvedTargetPage - livePageBeforeApply) <= 1
     }