feat(tickets): attribution d'un sprint à la création via popup SprintPicker (#38)

Nouveau composant SprintPicker permettant de choisir un sprint lors de
la création d'un ticket depuis TicketsPanel ; export ajouté à l'index
des features tickets. Frontend-pur.

QA vert : tsc --noEmit exit 0, vitest 63 fichiers / 634 tests passés.

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

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

@@ -214,6 +214,80 @@ describe("TicketsView", () => {
     expect(await screen.findByText("Live created")).toBeTruthy();
   });
 
+  it("creates a ticket and assigns the sprint chosen via the picker (#38)", async () => {
+    ticket._seedSprint(PROJECT_ID, { id: "s1", order: 1, name: "Alpha" });
+    const setSpy = vi.spyOn(ticket, "setTicketSprint");
+
+    renderView(ticket, system, agent);
+    fireEvent.click(await screen.findByRole("button", { name: "New" }));
+    fireEvent.change(screen.getByLabelText("new ticket title"), {
+      target: { value: "With sprint" },
+    });
+
+    // Field defaults to "Sans sprint"; open the picker and pick Alpha.
+    const sprintField = screen.getByLabelText("choose sprint for new ticket");
+    expect(sprintField.textContent).toContain("Sans sprint");
+    fireEvent.click(sprintField);
+    fireEvent.click(await screen.findByLabelText("select sprint Alpha"));
+    expect(
+      screen.getByLabelText("choose sprint for new ticket").textContent,
+    ).toContain("Alpha");
+
+    fireEvent.click(screen.getByRole("button", { name: "Create" }));
+
+    // create → setTicketSprint(projectId, ref, "s1", version).
+    await waitFor(() => expect(setSpy).toHaveBeenCalledTimes(1));
+    const call = setSpy.mock.calls[0];
+    expect(call[0]).toBe(PROJECT_ID);
+    expect(call[2]).toBe("s1");
+    await waitFor(async () => {
+      const fresh = await ticket.read(PROJECT_ID, call[1]);
+      expect(fresh.sprintId).toBe("s1");
+    });
+  });
+
+  it("creates a ticket without a sprint — setTicketSprint is not called (#38)", async () => {
+    const setSpy = vi.spyOn(ticket, "setTicketSprint");
+
+    renderView(ticket, system, agent);
+    fireEvent.click(await screen.findByRole("button", { name: "New" }));
+    fireEvent.change(screen.getByLabelText("new ticket title"), {
+      target: { value: "No sprint" },
+    });
+    fireEvent.click(screen.getByRole("button", { name: "Create" }));
+
+    await waitFor(async () => {
+      const list = await ticket.list(PROJECT_ID);
+      expect(list.items.map((i) => i.title)).toContain("No sprint");
+    });
+    expect(setSpy).not.toHaveBeenCalled();
+  });
+
+  it("keeps the created ticket and surfaces the error when sprint assignment fails (#38)", async () => {
+    ticket._seedSprint(PROJECT_ID, { id: "s1", order: 1, name: "Alpha" });
+    vi.spyOn(ticket, "setTicketSprint").mockRejectedValueOnce({
+      code: "INTERNAL",
+      message: "assign boom",
+    });
+
+    renderView(ticket, system, agent);
+    fireEvent.click(await screen.findByRole("button", { name: "New" }));
+    fireEvent.change(screen.getByLabelText("new ticket title"), {
+      target: { value: "Kept anyway" },
+    });
+    fireEvent.click(screen.getByLabelText("choose sprint for new ticket"));
+    fireEvent.click(await screen.findByLabelText("select sprint Alpha"));
+    fireEvent.click(screen.getByRole("button", { name: "Create" }));
+
+    // The ticket was created despite the failed assignment (no data lost)…
+    await waitFor(async () => {
+      const list = await ticket.list(PROJECT_ID);
+      expect(list.items.map((i) => i.title)).toContain("Kept anyway");
+    });
+    // …and the assignment failure is surfaced.
+    expect(await screen.findByText(/assign boom/)).toBeTruthy();
+  });
+
   it("multi-selects status/priority facets (OR intra, AND inter) and clears (#12)", async () => {
     const listSpy = vi.spyOn(ticket, "list");
     await ticket.create(PROJECT_ID, {