fix(ticket #7): ajoute le bouton Annuler aux notifications de fin de background task

frontend/src/features/projects/ProjectsView.ls7.test.tsx

@@ -268,7 +268,7 @@ describe("ProjectsView — LS7 conversation viewer integration", () => {
     const toast = await screen.findByRole("button", {
       name: /Appel Main -> DevBackend terminé/i,
     });
-    expect(within(toast).getByText("Task task-ren")).toBeTruthy();
+    expect(within(toast).getByText("alpha · Task task-ren")).toBeTruthy();
 
     fireEvent.click(toast);
 
@@ -346,7 +346,7 @@ describe("ProjectsView — LS7 conversation viewer integration", () => {
     const toast = await screen.findByRole("button", {
       name: /Background task failed/i,
     });
-    expect(within(toast).getByText("agent-ge · task-gen")).toBeTruthy();
+    expect(within(toast).getByText("alpha · agent-ge · task-gen")).toBeTruthy();
 
     fireEvent.click(toast);
 
@@ -355,4 +355,38 @@ describe("ProjectsView — LS7 conversation viewer integration", () => {
     ).toBeNull();
     expect(await screen.findByText("Work")).toBeTruthy();
   });
+
+  it("prefixes task toast context with a truncatable project-name line and falls back when unresolved", async () => {
+    const project = new MockProjectGateway();
+    const created = await project.createProject(
+      "alpha with a very long project name that must stay on one line",
+      "/p/a",
+    );
+    const system = new MockSystemGateway();
+    renderView(project, { system });
+
+    await openProjectAndWorkTab("/p/a");
+    system.emit({
+      type: "backgroundTaskChanged",
+      projectId: created.id,
+      agentId: "agent-long-name-context",
+      taskId: "task-long-name-context",
+      state: "completed",
+    });
+    system.emit({
+      type: "backgroundTaskChanged",
+      projectId: "project-not-in-view",
+      agentId: "agent-fallback-context",
+      taskId: "task-fallback-context",
+      state: "failed",
+    });
+
+    const longNameLine = await screen.findByText(
+      "alpha with a very long project name that must stay on one line · agent-lo · task-lon",
+    );
+    expect(longNameLine.className).toContain("truncate");
+    expect(
+      await screen.findByText("Projet inconnu · agent-fa · task-fal"),
+    ).toBeTruthy();
+  });
 });