Address feedback

Author: jasonpaulos

src/Microsoft.ComponentDetection.Orchestrator/Services/GraphTranslation/DefaultGraphTranslationService.cs

@@ -141,9 +141,18 @@ private static void PruneFilteredComponentsFromGraphs(DependencyGraphCollection
             }
 
             // Remove references to removed IDs from remaining nodes' dependency sets.
-            foreach (var edges in graph.Values)
+            // Normalize empty edge sets to null for consistent leaf-node serialization.
+            foreach (var nodeId in graph.Keys.ToList())
             {
-                edges?.RemoveWhere(id => !retainedIds.Contains(id));
+                var edges = graph[nodeId];
+                if (edges != null)
+                {
+                    edges.RemoveWhere(id => !retainedIds.Contains(id));
+                    if (edges.Count == 0)
+                    {
+                        graph[nodeId] = null;
+                    }
+                }
             }
 
             // Clean up metadata sets.

test/Microsoft.ComponentDetection.Orchestrator.Tests/Services/DefaultGraphTranslationServiceTests.cs

@@ -731,9 +731,9 @@ public void FilterBaseImageComponents_PrunesFilteredComponentsFromDependencyGrap
         graph.Should().ContainKey(retainedComponent.Component.Id);
         graph.Should().NotContainKey(baseImageComponent.Component.Id);
 
-        // The retained component's edge set should not reference the removed component.
+        // The retained component should be a leaf node (null edges) after its only dependency was pruned.
         var retainedEdges = graph[retainedComponent.Component.Id];
-        retainedEdges?.Should().NotContain(baseImageComponent.Component.Id);
+        retainedEdges.Should().BeNull();
 
         // Metadata sets should also be cleaned.
         graphEntry.Value.ExplicitlyReferencedComponentIds.Should().NotContain(baseImageComponent.Component.Id);