fix(sync): Don't spread stale metadata when pulling commit from remote

When pulling commit metadata from remote, only set the commit field
rather than spreading parent.metadata. The stale integration metadata
in parent.metadata would overwrite fresh state from result.metadata
in saveMetadata, reverting issue state changes.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: dcramer

src/core/github/sync.ts

@@ -332,9 +332,10 @@ export class GitHubSyncService {
             }
 
             // Pull commit metadata if present in remote
+            // Only set the commit field - don't spread parent.metadata as it may contain
+            // stale integration metadata that would overwrite fresh state in saveMetadata
             if (remoteMetadata.commit?.sha && !parent.metadata?.commit?.sha) {
               localUpdates.metadata = {
-                ...parent.metadata,
                 commit: remoteMetadata.commit,
               };
             }
@@ -363,7 +364,6 @@ export class GitHubSyncService {
         }
       }
 
-
       // Check if we can skip this update by comparing with GitHub
       if (skipUnchanged) {
         const expectedBody = this.renderBody(parent, descendants);