feat(FN-3082): restructure dependency graph plugin with modular architectur

Implements a modular dependency graph feature for the Fusion dashboard plugin, replacing the monolithic `DependencyGraphView` component with a factored architecture: graph types and filtering (Step 1), a data hook (Step 2), auto-layout engine (Step 3), SVG edge rendering (Step 4), an interaction hoo

Fusion-Task-Id: FN-3082

plugins/fusion-plugin-dependency-graph/src/useGraphData.ts

@@ -0,0 +1,17 @@
+import { useMemo } from "react";
+import type { Task } from "@fusion/core";
+import type { GraphData, GraphNode } from "./types";
+
+export function useGraphData(tasks: Task[]): GraphData {
+  return useMemo(() => {
+    const nodes: GraphNode[] = tasks.map((task) => ({ task }));
+    const taskIds = new Set(tasks.map((task) => task.id));
+    const edges = tasks.flatMap((task) =>
+      (task.dependencies ?? [])
+        .filter((dependencyId) => taskIds.has(dependencyId))
+        .map((dependencyId) => ({ source: task.id, target: dependencyId })),
+    );
+
+    return { nodes, edges };
+  }, [tasks]);
+}