fix(percy): add relationships.resources to snapshot creation in clone

Percy API requires relationships field even for screenshot builds.
Empty resources array is valid for app/screenshot type snapshots.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: DeRaowl

src/tools/percy-mcp/v2/clone-build.ts

@@ -466,7 +466,11 @@ async function copyScreenshots(
         `/builds/${buildId}/snapshots`,
         token,
         {
-          data: { type: "snapshots", attributes: { name: snap.name } },
+          data: {
+            type: "snapshots",
+            attributes: { name: snap.name },
+            relationships: { resources: { data: [] } },
+          },
         },
       );
       const newSnapId = snapResult?.data?.id;