feat(tickets): ajoute les pièces jointes sur tickets (#108)

Stockage flat côté ticket + métadonnées d'attachments, lecture exposée côté
backend/MCP, et UI minimale de liste/ajout dans TicketDetail. Traverse le
domaine (Issue, ports), l'application (usecases + assistant de ticket), les
adaptateurs infra/MCP (issues store, orchestrateur), les DTO backend/web-
server/app-tauri, et le frontend (domain/ports/adapters/hooks/UI).

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

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

@@ -172,6 +172,46 @@ describe("MockTicketGateway", () => {
     ).rejects.toMatchObject({ message: expect.stringContaining("version conflict") });
   });
 
+  it("adds ticket attachments and marks them summarized (#108)", async () => {
+    const t = await ticket.create(PROJECT_ID, { title: "With attachment" });
+
+    const attached = await ticket.addAttachment(
+      PROJECT_ID,
+      t.ref,
+      "/tmp/spec.pdf",
+      t.version,
+      "application/pdf",
+    );
+    expect(attached.version).toBe(2);
+    expect(attached.attachments).toMatchObject([
+      {
+        filename: "spec.pdf",
+        mime: "application/pdf",
+        summarizedInCarnet: false,
+      },
+    ]);
+
+    const content = await ticket.readAttachment(
+      PROJECT_ID,
+      t.ref,
+      attached.attachments[0].id,
+    );
+    expect(content.attachment.filename).toBe("spec.pdf");
+    expect(content.contentBase64).toBeTruthy();
+
+    const summarized = await ticket.markAttachmentSummarized(
+      PROJECT_ID,
+      t.ref,
+      attached.attachments[0].id,
+      attached.version,
+    );
+    expect(summarized.version).toBe(3);
+    expect(summarized.attachments[0]).toMatchObject({
+      summarizedInCarnet: true,
+      summarizedBy: { kind: "user" },
+    });
+  });
+
   it("deletes a ticket, removing it and emitting issueDeleted with freedSprint (#6)", async () => {
     ticket._seedSprint(PROJECT_ID, { id: "s1", order: 1, name: "S" });
     const t = await ticket.create(PROJECT_ID, { title: "Doomed" });
@@ -515,6 +555,36 @@ describe("TicketsView", () => {
     });
   });
 
+  it("shows, adds, and marks ticket attachments from the detail (#108)", async () => {
+    const t = await ticket.create(PROJECT_ID, { title: "Attachable" });
+    renderView(ticket, system, agent);
+
+    fireEvent.click(await screen.findByText("Attachable"));
+    const dialog = await screen.findByRole("dialog", { name: `ticket ${t.ref}` });
+
+    expect(within(dialog).getByText("Pièces jointes")).toBeTruthy();
+    expect(within(dialog).getByText("Aucune pièce jointe.")).toBeTruthy();
+
+    fireEvent.click(within(dialog).getByText("Joindre"));
+
+    expect(await within(dialog).findByText("mock-attachment.txt")).toBeTruthy();
+    expect(within(dialog).getByText(/text\/plain/)).toBeTruthy();
+    expect(within(dialog).getByText("Résumé : non")).toBeTruthy();
+
+    const attached = await ticket.read(PROJECT_ID, t.ref);
+    expect(attached.attachments).toHaveLength(1);
+
+    fireEvent.click(
+      within(dialog).getByLabelText("marquer résumé mock-attachment.txt"),
+    );
+
+    expect(await within(dialog).findByText("Résumé : oui")).toBeTruthy();
+    await waitFor(async () => {
+      const fresh = await ticket.read(PROJECT_ID, t.ref);
+      expect(fresh.attachments[0].summarizedInCarnet).toBe(true);
+    });
+  });
+
   it("assigns only known project agents", async () => {
     const known = await seedAgent(agent, "Backend");
     const t = await ticket.create(PROJECT_ID, { title: "Assignable" });