Fix circular dependency detection and hide empty graph modal

- Add artifact-level self-dependency check (skip if dep resolves to same artifact)
- Close dependency graph modal if package has no dependencies to show
  (only root package with no children and no missing deps)

frontend/src/components/DependencyGraph.tsx

@@ -117,6 +117,14 @@ function DependencyGraph({ projectName, packageName, tagName, onClose }: Depende
 
       try {
         const result = await resolveDependencies(projectName, packageName, tagName);
+
+        // If only the root package (no dependencies) and no missing deps, close the modal
+        const hasDeps = result.artifact_count > 1 || (result.missing && result.missing.length > 0);
+        if (!hasDeps) {
+          onClose();
+          return;
+        }
+
         setResolution(result);
 
         const graph = await buildGraph(result);