fix(sync): serialize rebuild cache and avoid transient empty mapping

Acquire an exclusive sync lock during rebuildCache and release it in finally, while removing the intermediate taskFileMapping clear step that could be persisted by debounced saves. This keeps rebuild atomic from reader and persistence perspectives.

src/data/cache.ts

@@ -709,7 +709,18 @@ export class CacheOperation   {
      */
     async rebuildCache(noticeCallback?: (message: string) => void): Promise<RebuildCacheResult> {
         const backupMapping = { ...this.plugin.settings.taskFileMapping };
+        let exclusiveLockAcquired = false;
         try {
+            const syncLockManager = this.plugin.syncLockManager;
+            if (!syncLockManager) {
+                throw new Error('Sync lock manager is not initialized');
+            }
+
+            exclusiveLockAcquired = await syncLockManager.acquireExclusive();
+            if (!exclusiveLockAcquired) {
+                throw new Error('Unable to acquire sync lock for cache rebuild. Please retry in a few seconds.');
+            }
+
             if (noticeCallback) {
                 noticeCallback('Starting cache rebuild...');
             } else {
@@ -718,18 +729,11 @@ export class CacheOperation   {
             this.plugin.logOperation?.log('CACHE_REBUILT', 'Starting cache rebuild...');
 
             // ==========================================================================================
-            // Step 1: 清空 taskFileMapping
             // ==========================================================================================
             // 
             // 【说明】
-            // taskFileMapping 是从任务 ID 到文件位置的映射
-            // 重建缓存时需要重新扫描，所以先清空
-            // fileMetadata 保留，因为文件本身可能还在
             // 
             // ==========================================================================================
-            
-            // Step 1: Backup old mapping, then clear (restore on failure)
-            await this.plugin.safeSettings?.update({ taskFileMapping: {} }, false);
 
             // ==========================================================================================
             // Step 2: 确保 syncData 已加载
@@ -1118,6 +1122,10 @@ export class CacheOperation   {
                 new Notice(message);
             }
             return { success: false, tasksProcessed: 0, conflictsCount: 0, nonActiveCount: 0, issueCount: 0, convertedCount: 0, tasksWithoutIdCount: 0 };
+        } finally {
+            if (exclusiveLockAcquired) {
+                this.plugin.syncLockManager?.release();
+            }
         }
     }
 

src/sync/syncLock.ts

@@ -37,6 +37,27 @@ export class SyncLockManager {
 		return !this.plugin.saveLock;
 	}
 
+	async acquireExclusive(): Promise<boolean> {
+		if (this.plugin.saveLock) {
+			this.plugin.debugLog('save locked, waiting before exclusive sync acquire.');
+			const saveReleased = await this.waitForSaveRelease();
+			if (!saveReleased) {
+				this.plugin.debugLog('save lock did not release in time.');
+				return false;
+			}
+		}
+
+		if (this.locked) {
+			this.plugin.debugLog('sync locked. waiting for exclusive acquire.');
+			const released = await this.waitForRelease();
+			if (!released) return false;
+			this.plugin.debugLog('sync unlocked.');
+		}
+
+		this.locked = true;
+		return true;
+	}
+
 
 	async acquire(direction?: SyncDirection): Promise<boolean> {
 		if (!this.plugin.settings.syncEnabled) {