feat(sprints): surface frontend du modèle de sprints

Ticket #10 — volet frontend des sprints.

- Domaine et ports frontend étendus au modèle de sprints (domain/index.ts,
  ports/index.ts).
- Adaptateurs : ticket.ts et mock/index.ts câblent les opérations sprints.
- UI tickets : useTickets + TicketsPanel exposent le rattachement/gestion des
  sprints, avec tests Vitest associés.

Typecheck / vitest / build verts.

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

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

@@ -347,6 +347,71 @@ describe("TicketsView", () => {
     await waitFor(() => expect(onClose).toHaveBeenCalledTimes(1));
   });
 
+  it("groups tickets by sprint with a « Sans sprint » bucket (#10)", async () => {
+    // Two ordered sprints + one ticket in each + one loose ticket.
+    ticket._seedSprint(PROJECT_ID, { id: "s1", order: 1, name: "Sprint One" });
+    ticket._seedSprint(PROJECT_ID, { id: "s2", order: 2, name: "Sprint Two" });
+    const t1 = await ticket.create(PROJECT_ID, { title: "In one" });
+    const t2 = await ticket.create(PROJECT_ID, { title: "In two" });
+    await ticket.create(PROJECT_ID, { title: "Loose" });
+    await ticket.setTicketSprint(PROJECT_ID, t1.ref, "s1", t1.version);
+    await ticket.setTicketSprint(PROJECT_ID, t2.ref, "s2", t2.version);
+
+    renderView(ticket, system, agent);
+
+    // Sections appear in sprint `order`, then the "Sans sprint" bucket last.
+    await screen.findByRole("region", { name: "sprint section Sprint One" });
+    const sections = screen
+      .getAllByRole("region")
+      .map((r) => r.getAttribute("aria-label"))
+      .filter((l) => l?.startsWith("sprint section"));
+    expect(sections).toEqual([
+      "sprint section Sprint One",
+      "sprint section Sprint Two",
+      "sprint section Sans sprint",
+    ]);
+
+    // The loose ticket lives in the bucket, the others under their sprint.
+    const bucket = screen.getByRole("region", { name: "sprint section Sans sprint" });
+    expect(within(bucket).getByText("Loose")).toBeTruthy();
+    const one = screen.getByRole("region", { name: "sprint section Sprint One" });
+    expect(within(one).getByText("In one")).toBeTruthy();
+  });
+
+  it("assigns a ticket to a sprint via the row selector (#10)", async () => {
+    ticket._seedSprint(PROJECT_ID, { id: "s1", order: 1, name: "Sprint One" });
+    const t = await ticket.create(PROJECT_ID, { title: "Movable" });
+
+    renderView(ticket, system, agent);
+
+    // It starts in the "Sans sprint" bucket.
+    const bucket = await screen.findByRole("region", {
+      name: "sprint section Sans sprint",
+    });
+    expect(within(bucket).getByText("Movable")).toBeTruthy();
+
+    // Pick the sprint in the row selector → assign it.
+    fireEvent.change(screen.getByLabelText(`sprint for ${t.ref}`), {
+      target: { value: "s1" },
+    });
+
+    // The gateway recorded the membership…
+    await waitFor(async () => {
+      const fresh = await ticket.read(PROJECT_ID, t.ref);
+      expect(fresh.sprintId).toBe("s1");
+    });
+    // …and the UI regrouped it under Sprint One, emptying the bucket.
+    await waitFor(() => {
+      const one = screen.getByRole("region", {
+        name: "sprint section Sprint One",
+      });
+      expect(within(one).getByText("Movable")).toBeTruthy();
+    });
+    expect(
+      screen.queryByRole("region", { name: "sprint section Sans sprint" }),
+    ).toBeNull();
+  });
+
   it("copies a delegation context prompt (F7)", async () => {
     const writeText = stubClipboard();
     const t = await ticket.create(PROJECT_ID, { title: "Delegate me" });