fix: report nested workspace conflicts

frontend/src/shell/WorkspacePublishDialog.test.tsx

@@ -30,6 +30,18 @@ const conflict: WorkspaceConflict = {
   remote: { ...workspace, semantic_index: { ...workspace.semantic_index, embedding: { ...workspace.semantic_index.embedding, model: "remote-model" } } },
 };
 
+const diagnosticsBranchConflict: WorkspaceConflict = {
+  ...conflict,
+  fields: ["diagnostics.dwh_rest"],
+  base: workspace,
+  remote: workspace,
+  local: {
+    ...workspace,
+    dwh: { ...workspace.dwh, supported_transports: ["postgres_direct", "rest_api"] },
+    diagnostics: { dwh_rest: { method: "GET", path: "/health", auth: "none", response: { database: "database", schema: "schema" } } },
+  },
+};
+
 beforeEach(() => {
   server.use(http.post("http://localhost:8787/workspaces/validate", () => HttpResponse.json({ workspace, contract: {} })));
 });
@@ -101,6 +113,26 @@ test("saves explicit local choices as a rebased draft and does not republish it"
   expect(publishCalls).toBe(1);
 });
 
+test("rebases a selected optional diagnostics branch into the revised draft", async () => {
+  const user = userEvent.setup();
+  const saved = vi.fn();
+  server.use(http.post("http://localhost:8787/workspaces/publish", () => HttpResponse.json({
+    ...diagnosticsBranchConflict, message: "Workspace changed in the registry.",
+  }, { status: 409 })));
+  render(<WorkspacePublishDialog open request={request} onOpenChange={vi.fn()} onPublished={vi.fn()} onResolved={saved} onPull={vi.fn()} onReload={vi.fn()} />);
+
+  await user.click(screen.getByRole("button", { name: "Validate draft" }));
+  await user.click(await screen.findByRole("button", { name: "Publish" }));
+  await user.click(screen.getByRole("button", { name: "Confirm publish" }));
+  await user.click(await screen.findByRole("radio", { name: "Use your draft for diagnostics.dwh_rest" }));
+  await user.click(screen.getByRole("button", { name: "Save revised draft" }));
+
+  expect(saved).toHaveBeenCalledWith(expect.objectContaining({
+    baseCommit: "c".repeat(40), baseBlob: "d".repeat(40),
+    workspace: expect.objectContaining({ diagnostics: diagnosticsBranchConflict.local.diagnostics }),
+  }));
+});
+
 test("keeps a conflict open and redacts a failed registry pull", async () => {
   const user = userEvent.setup();
   server.use(http.post("http://localhost:8787/workspaces/publish", () => HttpResponse.json({