feat(cli): références d'attachments [file n]/[image n] dans le transcript + zone chat redimensionnable — #188 (QA verte)

- Attachments: projection canonique ChatPromptAttachmentDto (référence [file n]/[image n] par compteur de type, ordre d'import) insérée dans le prompt modèle et transportée par ReplyChunk::UserPrompt (attachmentRefs) ; rendu compact côté CustomAgentChatView.
- Resize: la zone chat (LeafView/LayoutGrid) est redimensionnable, taille actuelle conservée par défaut, préférence locale persistée.
- Tests: commands (projection des refs), dto_chat, chat_bridge, CustomAgentChatView, LayoutGrid.chat.

frontend/src/features/layout/LayoutGrid.chat.test.tsx

@@ -180,6 +180,37 @@ describe("LayoutGrid custom agent CLI (#147)", () => {
     expect(screen.getAllByText(/mock-attachment.txt/).length).toBeGreaterThan(0);
   });
 
+  it("resizes the custom CLI chat locally per cell and can reset to the default size", async () => {
+    const gateways = await seeded(structuredProfile);
+    const layout = gateways.layout as MockLayoutGateway;
+    const tree = await layout.loadLayout("p1");
+    const leafId = leaves(tree)[0].id;
+    window.localStorage.setItem(`idea.agent-cell-mode.p1.${leafId}`, "custom");
+
+    renderGrid(gateways);
+
+    const shell = await screen.findByTestId("custom-agent-chat-shell");
+    expect(shell.style.width).toBe("100%");
+    expect(window.localStorage.getItem(`idea.custom-chat-size.p1.${leafId}`)).toBeNull();
+
+    fireEvent.mouseDown(screen.getByRole("button", { name: `resize custom chat ${leafId}` }), {
+      clientX: 0,
+      clientY: 0,
+    });
+    fireEvent.mouseMove(window, { clientX: 640, clientY: 420 });
+    fireEvent.mouseUp(window);
+
+    await waitFor(() => expect(shell.style.width).toBe("640px"));
+    expect(shell.style.height).toBe("420px");
+    expect(JSON.parse(window.localStorage.getItem(`idea.custom-chat-size.p1.${leafId}`) ?? "{}"))
+      .toEqual({ width: 640, height: 420 });
+
+    fireEvent.click(screen.getByRole("button", { name: `reset custom chat size ${leafId}` }));
+
+    await waitFor(() => expect(shell.style.width).toBe("100%"));
+    expect(window.localStorage.getItem(`idea.custom-chat-size.p1.${leafId}`)).toBeNull();
+  });
+
   it("opens the custom CLI even when the agent already has a structured background session (#169)", async () => {
     const layout = new MockLayoutGateway();
     const agent = new MockAgentGateway();