feat(FN-3090): add graph position persistence to dependency graph plugin

Merges graph position persistence into the dependency graph plugin (FN-3090) via a scoped storage layer, a dedicated position storage utility, and a React hook that preserves pan/zoom state across sessions. Also includes a responsive CSS fix for ScriptsModal and supporting test coverage in both the

Fusion-Task-Id: FN-3090

plugins/fusion-plugin-dependency-graph/src/__tests__/useGraphPositions.test.ts

@@ -0,0 +1,66 @@
+import { act, renderHook } from "@testing-library/react";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { useGraphPositions } from "../hooks/useGraphPositions";
+import * as storage from "../utils/graphPositionStorage";
+
+vi.mock("../utils/graphPositionStorage", () => ({
+  loadPositions: vi.fn(),
+  savePositions: vi.fn(),
+  clearPositions: vi.fn(),
+}));
+
+describe("useGraphPositions", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("loads saved positions on mount with project scope", () => {
+    vi.mocked(storage.loadPositions).mockReturnValue({ a: { x: 1, y: 2 } });
+
+    const { result } = renderHook(() => useGraphPositions({ projectId: "p1", visibleTaskIds: new Set(["a"]) }));
+
+    expect(storage.loadPositions).toHaveBeenCalledWith("p1");
+    expect(result.current.savedPositions).toEqual({ a: { x: 1, y: 2 } });
+  });
+
+  it("reloads positions when project id changes", () => {
+    vi.mocked(storage.loadPositions).mockReturnValueOnce({ a: { x: 1, y: 1 } }).mockReturnValueOnce({ b: { x: 2, y: 2 } });
+
+    const { result, rerender } = renderHook(
+      ({ projectId }) => useGraphPositions({ projectId, visibleTaskIds: new Set(["a", "b"]) }),
+      { initialProps: { projectId: "p1" } },
+    );
+
+    rerender({ projectId: "p2" });
+
+    expect(storage.loadPositions).toHaveBeenNthCalledWith(1, "p1");
+    expect(storage.loadPositions).toHaveBeenNthCalledWith(2, "p2");
+    expect(result.current.savedPositions).toEqual({ b: { x: 2, y: 2 } });
+  });
+
+  it("persistPositions writes scoped and filters non-visible ids", () => {
+    vi.mocked(storage.loadPositions).mockReturnValue({});
+
+    const { result } = renderHook(() => useGraphPositions({ projectId: "p1", visibleTaskIds: new Set(["a"]) }));
+
+    act(() => {
+      result.current.persistPositions({ a: { x: 1, y: 2 }, hidden: { x: 9, y: 9 } });
+    });
+
+    expect(storage.savePositions).toHaveBeenCalledWith({ a: { x: 1, y: 2 }, hidden: { x: 9, y: 9 } }, new Set(["a"]), "p1");
+    expect(result.current.savedPositions).toEqual({ a: { x: 1, y: 2 } });
+  });
+
+  it("clearSavedPositions clears storage and resets state", () => {
+    vi.mocked(storage.loadPositions).mockReturnValue({ a: { x: 1, y: 2 } });
+
+    const { result } = renderHook(() => useGraphPositions({ projectId: "p1", visibleTaskIds: new Set(["a"]) }));
+
+    act(() => {
+      result.current.clearSavedPositions();
+    });
+
+    expect(storage.clearPositions).toHaveBeenCalledWith("p1");
+    expect(result.current.savedPositions).toBeNull();
+  });
+});