feat(sprints): interface de création et gestion des sprints (frontend)

Ticket #11 — surface UI de gestion des sprints (frontend pur).

- Nouveau composant SprintManager : création (nom optionnel), édition et
  gestion du cycle de vie d'un sprint, contrôles accessibles (pas de DnD).
- useTickets étendu aux opérations de gestion de sprint ; ports, adaptateurs
  (ticket.ts, mock/index.ts) et TicketsPanel câblés en conséquence.
- Tests Vitest associés (tickets.test.tsx).

Typecheck / vitest (497+ tests) / build verts.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/features/tickets/tickets.test.tsx

@@ -428,3 +428,155 @@ describe("TicketsView", () => {
     );
   });
 });
+
+describe("SprintManager (#11)", () => {
+  let system: MockSystemGateway;
+  let ticket: MockTicketGateway;
+  let agent: MockAgentGateway;
+
+  beforeEach(() => {
+    system = new MockSystemGateway();
+    ticket = new MockTicketGateway(system);
+    agent = new MockAgentGateway();
+  });
+
+  /** Renders the view and opens the sprint-management overlay. */
+  async function openManager(): Promise<HTMLElement> {
+    renderView(ticket, system, agent);
+    await waitFor(() =>
+      expect(
+        screen.getByRole("button", { name: "manage sprints" }),
+      ).toBeTruthy(),
+    );
+    fireEvent.click(screen.getByRole("button", { name: "manage sprints" }));
+    return screen.findByRole("dialog", { name: "manage sprints" });
+  }
+
+  it("creates a sprint", async () => {
+    const dialog = await openManager();
+
+    fireEvent.change(within(dialog).getByLabelText("new sprint name"), {
+      target: { value: "Alpha" },
+    });
+    fireEvent.click(within(dialog).getByText("Create sprint"));
+
+    await waitFor(async () => {
+      const sprints = await ticket.listSprints(PROJECT_ID);
+      expect(sprints.map((s) => s.name)).toEqual(["Alpha"]);
+    });
+    expect(
+      await within(dialog).findByLabelText("sprint row Alpha"),
+    ).toBeTruthy();
+  });
+
+  it("creates a sprint with a default positional name when the name is empty", async () => {
+    const dialog = await openManager();
+
+    // Leave the name field empty and create → default "Sprint N" (here N=1).
+    expect(
+      (within(dialog).getByLabelText("new sprint name") as HTMLInputElement)
+        .value,
+    ).toBe("");
+    fireEvent.click(within(dialog).getByText("Create sprint"));
+
+    await waitFor(async () => {
+      const sprints = await ticket.listSprints(PROJECT_ID);
+      expect(sprints.map((s) => s.name)).toEqual(["Sprint 1"]);
+    });
+    expect(
+      await within(dialog).findByLabelText("sprint row Sprint 1"),
+    ).toBeTruthy();
+  });
+
+  it("renames a sprint", async () => {
+    ticket._seedSprint(PROJECT_ID, { id: "s1", order: 1, name: "Old" });
+    const dialog = await openManager();
+
+    fireEvent.change(
+      await within(dialog).findByLabelText("rename sprint Old"),
+      { target: { value: "New" } },
+    );
+    fireEvent.click(within(dialog).getByLabelText("save sprint Old"));
+
+    await waitFor(async () => {
+      const [s] = await ticket.listSprints(PROJECT_ID);
+      expect(s.name).toBe("New");
+    });
+  });
+
+  it("reorders sprints via the accessible down button", async () => {
+    ticket._seedSprint(PROJECT_ID, { id: "s1", order: 1, name: "One" });
+    ticket._seedSprint(PROJECT_ID, { id: "s2", order: 2, name: "Two" });
+    const dialog = await openManager();
+
+    fireEvent.click(
+      await within(dialog).findByLabelText("move sprint One down"),
+    );
+
+    await waitFor(async () => {
+      const sprints = await ticket.listSprints(PROJECT_ID);
+      // "Two" is now first (order 1), "One" second.
+      expect(sprints.map((s) => s.name)).toEqual(["Two", "One"]);
+    });
+  });
+
+  it("deletes a sprint and unassigns (does not delete) its tickets", async () => {
+    ticket._seedSprint(PROJECT_ID, { id: "s1", order: 1, name: "Doomed" });
+    const t = await ticket.create(PROJECT_ID, { title: "Kept" });
+    await ticket.setTicketSprint(PROJECT_ID, t.ref, "s1", t.version);
+
+    const dialog = await openManager();
+
+    fireEvent.click(
+      await within(dialog).findByLabelText("delete sprint Doomed"),
+    );
+    // The confirmation explains tickets are unassigned, not deleted.
+    const confirm = await screen.findByRole("dialog", {
+      name: "delete sprint confirmation",
+    });
+    expect(confirm.textContent).toMatch(/ne seront pas supprimés/i);
+    fireEvent.click(within(confirm).getByLabelText("confirm delete sprint"));
+
+    await waitFor(async () => {
+      expect(await ticket.listSprints(PROJECT_ID)).toHaveLength(0);
+    });
+    // The ticket still exists, just unassigned.
+    const fresh = await ticket.read(PROJECT_ID, t.ref);
+    expect(fresh.sprintId).toBeNull();
+    expect(fresh.title).toBe("Kept");
+  });
+
+  it("adds a backlog ticket to a sprint via the add selector", async () => {
+    ticket._seedSprint(PROJECT_ID, { id: "s1", order: 1, name: "Target" });
+    const t = await ticket.create(PROJECT_ID, { title: "Backlog item" });
+
+    const dialog = await openManager();
+
+    fireEvent.change(
+      await within(dialog).findByLabelText("add ticket to sprint Target"),
+      { target: { value: t.ref } },
+    );
+
+    await waitFor(async () => {
+      const fresh = await ticket.read(PROJECT_ID, t.ref);
+      expect(fresh.sprintId).toBe("s1");
+    });
+  });
+
+  it("removes a ticket from a sprint", async () => {
+    ticket._seedSprint(PROJECT_ID, { id: "s1", order: 1, name: "Holder" });
+    const t = await ticket.create(PROJECT_ID, { title: "Member" });
+    await ticket.setTicketSprint(PROJECT_ID, t.ref, "s1", t.version);
+
+    const dialog = await openManager();
+
+    fireEvent.click(
+      await within(dialog).findByLabelText(`remove ${t.ref} from sprint`),
+    );
+
+    await waitFor(async () => {
+      const fresh = await ticket.read(PROJECT_ID, t.ref);
+      expect(fresh.sprintId).toBeNull();
+    });
+  });
+});