FN-7125: add artifact route image integration coverage

Add integration coverage for task image artifacts flowing through the artifacts API.

- Add a real TaskStore-backed artifacts route integration test.
- Assert registered task image artifacts list with task metadata.
- Assert image media streams the registered bytes and content type.
- Cover empty task-scoped artifact listings.

Files changed:
 .../__tests__/artifacts-route-integration.test.ts  | 98 ++++++++++++++++++++++
 1 file changed, 98 insertions(+)

Fusion-Task-Id: FN-7125

Fusion-Task-Lineage: d79ccc2e-0819-4304-a757-c9d6a2aabb77

Co-authored-by: Fusion (runfusion.ai) <noreply@runfusion.ai>

packages/dashboard/src/routes/__tests__/artifacts-route-integration.test.ts

@@ -0,0 +1,98 @@
+// @vitest-environment node
+
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
+import express from "express";
+import { mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { TaskStore, type ArtifactWithTask } from "@fusion/core";
+import { createApiRoutes } from "../../routes.js";
+import { request as REQUEST } from "../../test-request.js";
+
+/*
+ * FNXC:ArtifactRegistry 2026-06-27-00:00:
+ * The mocked artifacts route tests skip the real listArtifacts LEFT JOIN and hand-write media files. This integration test uses a real TaskStore so the Documents Artifacts view contract is pinned end-to-end: registered image artifacts list with task metadata and stream from the real disk write path.
+ */
+describe("artifacts route integration", () => {
+  let store: TaskStore;
+  let rootDir: string;
+  let globalDir: string;
+  let app: express.Express;
+
+  beforeEach(async () => {
+    rootDir = mkdtempSync(join(tmpdir(), "artifacts-route-root-"));
+    globalDir = mkdtempSync(join(tmpdir(), "artifacts-route-global-"));
+    store = new TaskStore(rootDir, globalDir, { inMemoryDb: true });
+    await store.init();
+
+    app = express();
+    app.use(express.json());
+    app.use("/api", createApiRoutes(store));
+  });
+
+  afterEach(() => {
+    store.close();
+    rmSync(rootDir, { recursive: true, force: true });
+    rmSync(globalDir, { recursive: true, force: true });
+  });
+
+  async function createTaskImageArtifact() {
+    const task = await store.createTask({
+      title: "Render screenshot",
+      description: "Capture dashboard artifact rendering evidence",
+    });
+    const imageBytes = Buffer.from("PNG-FN-7125-route-integration-image-bytes", "utf8");
+    const artifact = await store.registerArtifact({
+      type: "image",
+      title: "Dashboard screenshot",
+      mimeType: "image/png",
+      data: imageBytes,
+      authorId: "agent-7125",
+      authorType: "agent",
+      taskId: task.id,
+    });
+    return { task, artifact, imageBytes };
+  }
+
+  it("an image artifact created on a task appears in the artifacts listing with task association", async () => {
+    const { task, artifact } = await createTaskImageArtifact();
+
+    const res = await REQUEST(app, "GET", "/api/artifacts");
+
+    expect(res.status).toBe(200);
+    const body = res.body as ArtifactWithTask[];
+    expect(body).toHaveLength(1);
+    expect(body[0]).toMatchObject({
+      id: artifact.id,
+      type: "image",
+      mimeType: "image/png",
+      title: "Dashboard screenshot",
+      authorId: "agent-7125",
+      taskId: task.id,
+      taskTitle: "Render screenshot",
+    });
+    expect(body[0].taskColumn).toBeTruthy();
+  });
+
+  it("the image artifact streams its real bytes with the correct content type", async () => {
+    const { artifact, imageBytes } = await createTaskImageArtifact();
+
+    const res = await REQUEST(app, "GET", `/api/artifacts/${artifact.id}/media`);
+
+    expect(res.status).toBe(200);
+    expect(res.headers["content-type"]).toBe("image/png");
+    expect(Buffer.from(res.body as string, "utf8")).toEqual(imageBytes);
+  });
+
+  it("a task with no artifacts lists as empty", async () => {
+    const task = await store.createTask({
+      title: "Render screenshot",
+      description: "Capture dashboard artifact rendering evidence",
+    });
+
+    const res = await REQUEST(app, "GET", `/api/artifacts?taskId=${encodeURIComponent(task.id)}`);
+
+    expect(res.status).toBe(200);
+    expect(res.body).toEqual([]);
+  });
+});