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/__tests__/useGraphInteraction.test.ts

@@ -0,0 +1,89 @@
+import { describe, expect, it } from "vitest";
+import { act, renderHook } from "@testing-library/react";
+import { useGraphInteraction } from "../useGraphInteraction";
+
+describe("useGraphInteraction", () => {
+  it("starts with default pan/zoom", () => {
+    const { result } = renderHook(() => useGraphInteraction());
+    expect(result.current.zoom).toBe(1);
+    expect(result.current.pan).toEqual({ x: 0, y: 0 });
+  });
+
+  it("clamps zoom between 0.1 and 3", () => {
+    const { result } = renderHook(() => useGraphInteraction());
+
+    act(() => {
+      for (let i = 0; i < 100; i += 1) result.current.zoomOut();
+    });
+    expect(result.current.zoom).toBe(0.1);
+
+    act(() => {
+      for (let i = 0; i < 100; i += 1) result.current.zoomIn();
+    });
+    expect(result.current.zoom).toBe(3);
+  });
+
+  it("fits single node", () => {
+    const { result } = renderHook(() => useGraphInteraction());
+    act(() => {
+      result.current.fitToGraph(new Map([["A", { x: 0, y: 0 }]]), 800, 600);
+    });
+
+    expect(result.current.zoom).toBeGreaterThan(0.1);
+    expect(result.current.zoom).toBeLessThanOrEqual(3);
+  });
+
+  it("fits wide graph", () => {
+    const { result } = renderHook(() => useGraphInteraction());
+    act(() => {
+      result.current.fitToGraph(new Map([
+        ["A", { x: 0, y: 0 }],
+        ["B", { x: 2000, y: 0 }],
+      ]), 800, 600);
+    });
+
+    expect(result.current.zoom).toBeLessThan(1);
+  });
+
+  it("fits tall graph", () => {
+    const { result } = renderHook(() => useGraphInteraction());
+    act(() => {
+      result.current.fitToGraph(new Map([
+        ["A", { x: 0, y: 0 }],
+        ["B", { x: 0, y: 2000 }],
+      ]), 800, 600);
+    });
+
+    expect(result.current.zoom).toBeLessThan(1);
+  });
+
+  it("resets when positions are empty", () => {
+    const { result } = renderHook(() => useGraphInteraction());
+
+    act(() => {
+      result.current.zoomIn();
+      result.current.onPointerDown(1, { x: 10, y: 10 });
+      result.current.onPointerMove(1, { x: 110, y: 60 }, 800, 600);
+      result.current.onPointerUp(1);
+      result.current.fitToGraph(new Map(), 800, 600);
+    });
+
+    expect(result.current.zoom).toBe(1);
+    expect(result.current.pan).toEqual({ x: 0, y: 0 });
+  });
+
+  it("resetView restores defaults", () => {
+    const { result } = renderHook(() => useGraphInteraction());
+
+    act(() => {
+      result.current.zoomIn();
+      result.current.onPointerDown(1, { x: 0, y: 0 });
+      result.current.onPointerMove(1, { x: 200, y: 200 }, 800, 600);
+      result.current.onPointerUp(1);
+      result.current.resetView();
+    });
+
+    expect(result.current.zoom).toBe(1);
+    expect(result.current.pan).toEqual({ x: 0, y: 0 });
+  });
+});