fix(SyncProcess): Don't associate concurrentCreations with multiple candidates

Signed-off-by: Marcel Klehr <mklehr@gmx.net>

Author: marcelklehr

src/lib/strategies/Default.ts

@@ -892,12 +892,24 @@ export default class SyncProcess {
     }, ACTION_CONCURRENCY)
 
     const findChainCacheForCreations = {}
+    // Each target-side concurrent creation may be merged with at most ONE source creation. Without
+    // this, two source creations that both canMergeWith the same target creation (e.g. duplicate
+    // titles/urls produced by fuzzing or by a previous reset) each call addMapping against the same
+    // target id; the second add evicts the first ("X will become unmapped"), orphaning a real item
+    // which is then silently dropped. Claim a target creation synchronously the moment it is matched
+    // (before any await) so a concurrent task cannot claim it too.
+    const claimedTargetCreations = new Set()
     await Parallel.each(sourceScanResult.CREATE.getActions(), async(action) => {
       const concurrentCreation = targetCreations.find(a => (
+        !claimedTargetCreations.has(a) &&
         action.payload.parentId === Mappings.mapParentId(mappingsSnapshot, a.payload, action.payload.location) &&
-        action.payload.canMergeWith(a.payload)
+        action.payload.canMergeWith(a.payload) &&
+        // Don't bind to a target creation that is already mapped to a *different* item — that bind
+        // would evict the existing mapping and orphan its counterpart.
+        !Mappings.wouldEvictUnrelatedMapping(mappingsSnapshot, action.payload, a.payload)
       ))
       if (concurrentCreation) {
+        claimedTargetCreations.add(concurrentCreation)
         // created on both the target and sourcely, try to reconcile
         const subScanner = new Scanner(
           this.mappings,