Fix: Return shard filename to prevent orphan deletion

The markOrphanedFiles function was deleting shard manifests because
they weren't included in the newFiles set. Now writeShardedCategory
returns the shard filename and packItemCategoryData includes it in
the returned filenames list.

Author: ErcinDedeoglu

src/sync/operations/push.ts

@@ -171,9 +171,10 @@ function packItemCategoryData(
   const newItems = removeItemsById(processed, tombResult.itemsToRemove);
 
   // Always use sharding for item categories
-  writeShardedCategory(category, newItems, tombResult.tombstones, ctx);
+  const shardFile = writeShardedCategory(category, newItems, tombResult.tombstones, ctx);
 
-  return filenames;
+  // Return both item filenames AND the shard file to prevent orphan deletion
+  return [...filenames, shardFile];
 }
 
 /**

src/sync/operations/sharding.ts

@@ -16,13 +16,14 @@ import type { PushContext, SyncCategory } from './types.js';
 
 /**
  * Write a sharded category (items stored in separate shard file).
+ * Returns the shard filename for tracking.
  */
 export function writeShardedCategory(
   category: SyncCategory,
   items: Record<string, ItemInfo>,
   tombstones: Record<string, Tombstone>,
   ctx: PushContext
-): void {
+): string {
   const shardFile = getShardFilename(category);
 
   // Create shard content
@@ -51,4 +52,6 @@ export function writeShardedCategory(
     lastModifiedBy: ctx.machineId,
     vectorClock: { [ctx.machineId]: ctx.newClock[ctx.machineId] ?? 1 },
   } satisfies ShardedCategoryRef;
+
+  return shardFile;
 }