fix(core): make Merkle root hashing deterministic

Build the Merkle DAG root from sorted file paths so identical file hash sets keep a stable root regardless of insertion order.

Author: wuyua9

packages/core/src/sync/synchronizer.test.ts

@@ -0,0 +1,28 @@
+import { FileSynchronizer } from './synchronizer';
+
+type TestableFileSynchronizer = {
+    buildMerkleDAG(fileHashes: Map<string, string>): {
+        rootIds: string[];
+    };
+};
+
+describe('FileSynchronizer Merkle DAG', () => {
+    it('uses stable root ids for identical file hashes inserted in different orders', () => {
+        const synchronizer = new FileSynchronizer('/tmp/project') as unknown as TestableFileSynchronizer;
+        const firstOrder = new Map([
+            ['src/a.ts', 'hash-a'],
+            ['src/b.ts', 'hash-b'],
+            ['README.md', 'hash-readme'],
+        ]);
+        const secondOrder = new Map([
+            ['README.md', 'hash-readme'],
+            ['src/b.ts', 'hash-b'],
+            ['src/a.ts', 'hash-a'],
+        ]);
+
+        const firstDag = synchronizer.buildMerkleDAG(firstOrder);
+        const secondDag = synchronizer.buildMerkleDAG(secondOrder);
+
+        expect(firstDag.rootIds).toEqual(secondDag.rootIds);
+    });
+});

packages/core/src/sync/synchronizer.ts

@@ -113,7 +113,7 @@ export class FileSynchronizer {
 
         // Create a root node for the entire directory
         let valuesString = "";
-        keys.forEach(key => {
+        sortedPaths.forEach(key => {
             valuesString += fileHashes.get(key);
         });
         const rootNodeData = "root:" + valuesString;