refactor: return shallow copies of nodes and edges from build()

build() was returning direct references to the builder's internal arrays, allowing callers to mutate graph.nodes or graph.edges and corrupt the builder's state. Spreading into new arrays at build time prevents this at negligible cost.

understand-anything-plugin/packages/core/src/analyzer/graph-builder.ts

@@ -412,8 +412,8 @@ export class GraphBuilder {
         analyzedAt: new Date().toISOString(),
         gitCommitHash: this.gitHash,
       },
-      nodes: this.nodes,
-      edges: this.edges,
+      nodes: [...this.nodes],
+      edges: [...this.edges],
       layers: [],
       tour: [],
     };