feat(tickets): fenêtre dédiée de gestion des tickets — liens via popup + assistant IA flottant (#17)

Lot C du sprint UI rework : fenêtre dédiée de gestion des tickets,
appuyée sur la primitive FloatingWindow (#16) et la popup TicketPicker (#18).

- TicketDetail : gestion des liens de ticket via la popup TicketPicker,
  assistant IA en fenêtre flottante
- FloatingWindow : ajustements pour l'usage fenêtre dédiée

Tests : tsc --noEmit clean, suite complète 530/530, suites tickets +
FloatingWindow 50/50.

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

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

@@ -645,47 +645,96 @@ describe("TicketsView", () => {
     );
 
     const detail = await screen.findByRole("dialog", { name: `ticket ${t.ref}` });
-    expect(within(detail).getByText("Assistant IA")).toBeTruthy();
 
-    const profileSelect = await within(detail).findByLabelText(
+    // The assistant is opened from the prominent bottom-right floating button;
+    // it is not inline anymore (#17).
+    expect(within(detail).queryByLabelText("profil de l'assistant")).toBeNull();
+    fireEvent.click(within(detail).getByLabelText("ouvrir l'assistant IA"));
+
+    // It opens in its own nested window.
+    const assistant = await screen.findByRole("dialog", {
+      name: `Assistant IA — ${t.ref}`,
+    });
+
+    const profileSelect = await within(assistant).findByLabelText(
       "profil de l'assistant",
     );
-    expect(within(detail).getByText("Ouvrir la conversation")).toBeTruthy();
+    expect(within(assistant).getByText("Ouvrir la conversation")).toBeTruthy();
 
     fireEvent.change(profileSelect, { target: { value: "qa-assistant" } });
-    fireEvent.click(within(detail).getByText("Ouvrir la conversation"));
+    fireEvent.click(within(assistant).getByText("Ouvrir la conversation"));
 
     expect(
-      await within(detail).findByLabelText("message à l'assistant"),
+      await within(assistant).findByLabelText("message à l'assistant"),
     ).toBeTruthy();
 
-    fireEvent.change(within(detail).getByLabelText("message à l'assistant"), {
+    fireEvent.change(within(assistant).getByLabelText("message à l'assistant"), {
       target: { value: "Crée un plan de correction" },
     });
-    fireEvent.click(within(detail).getByText("Envoyer"));
+    fireEvent.click(within(assistant).getByText("Envoyer"));
 
-    expect(await within(detail).findByText("Crée un plan de correction")).toBeTruthy();
     expect(
-      await within(detail).findByText(
+      await within(assistant).findByText("Crée un plan de correction"),
+    ).toBeTruthy();
+    expect(
+      await within(assistant).findByText(
         "Assistant: reçu « Crée un plan de correction ».",
       ),
     ).toBeTruthy();
 
-    fireEvent.click(within(detail).getByText("Fermer la conversation"));
+    fireEvent.click(within(assistant).getByText("Fermer la conversation"));
 
     await waitFor(() =>
       expect(
-        within(detail).queryByLabelText("message à l'assistant"),
+        within(assistant).queryByLabelText("message à l'assistant"),
       ).toBeNull(),
     );
-    expect(within(detail).getByText("Ouvrir la conversation")).toBeTruthy();
+    expect(within(assistant).getByText("Ouvrir la conversation")).toBeTruthy();
     expect(
-      within(detail).queryByText("Crée un plan de correction"),
+      within(assistant).queryByText("Crée un plan de correction"),
     ).toBeNull();
     expect(
-      within(detail).queryByText("Assistant: reçu « Crée un plan de correction »."),
+      within(assistant).queryByText(
+        "Assistant: reçu « Crée un plan de correction ».",
+      ),
     ).toBeNull();
   });
+
+  it("adds a link via the TicketPicker popup instead of a manual #id (#17)", async () => {
+    const a = await ticket.create(PROJECT_ID, { title: "Source ticket" });
+    const b = await ticket.create(PROJECT_ID, { title: "Target ticket" });
+    const gateways = { ticket, system, agent } as unknown as Gateways;
+
+    render(
+      <DIProvider gateways={gateways}>
+        <TicketDetail
+          projectId={PROJECT_ID}
+          ticketRef={a.ref}
+          onClose={() => {}}
+          onOpenRef={() => {}}
+        />
+      </DIProvider>,
+    );
+
+    const detail = await screen.findByRole("dialog", { name: `ticket ${a.ref}` });
+    // The old manual "#id" input is gone.
+    expect(within(detail).queryByLabelText("link target ref")).toBeNull();
+
+    // Choose the link kind, then open the picker and select the target ticket.
+    fireEvent.change(within(detail).getByLabelText("link kind"), {
+      target: { value: "blocks" },
+    });
+    fireEvent.click(within(detail).getByLabelText("add link"));
+
+    // The picker excludes the ticket itself; the target is offered.
+    expect(screen.queryByLabelText(`select ticket ${a.ref}`)).toBeNull();
+    fireEvent.click(await screen.findByLabelText(`select ticket ${b.ref}`));
+
+    await waitFor(async () => {
+      const fresh = await ticket.read(PROJECT_ID, a.ref);
+      expect(fresh.links).toEqual([{ targetRef: b.ref, kind: "blocks" }]);
+    });
+  });
 });
 
 describe("SprintManager (#11)", () => {