test(e2e): repoint document-chat spec to the Coach hand-off

The bespoke document-chat drawer was removed with Design A, so the old e2e
asserting the drawer overlay no longer applies. The spec now pins the
documents-side contract that replaced it: with a provider available the Coach
affordance hands off to the document-scoped Coach (/coach?doc=<id>), and with
no provider the AI area shows only the settings pointer and no Coach entry.

The Coach-side scope banner (the Document badge, "Chatting about", and the
not-indexed hint) moves to a coach-conversation component test, replacing the
drawer's not-indexed/render coverage; the fenced-send guarantee stays pinned by
the coach-send-target unit test.

src/components/insights/coach-panel/__tests__/coach-doc-scope-banner.test.tsx

@@ -0,0 +1,100 @@
+import { describe, it, expect, vi } from "vitest";
+import { renderToStaticMarkup } from "react-dom/server";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+
+// The page surface reads `useRouter` (Conversations routes via the app router).
+const pushMock = vi.fn();
+vi.mock("next/navigation", () => ({
+  useRouter: () => ({ push: pushMock }),
+}));
+
+import { I18nProvider } from "@/lib/i18n/context";
+import { queryKeys } from "@/lib/query-keys";
+import { CoachConversation } from "../coach-conversation";
+
+/**
+ * v1.28.51 (Documents R3, Design A) — the doc-scope banner.
+ *
+ * When the Coach is scoped to a document (the `/coach?doc=<id>` hand-off from
+ * the vault, before any thread exists), the shared `<CoachConversation>` surface
+ * paints a "Document" badge + "Chatting about: <title>" and, when the document
+ * is not yet content-indexed, the calm "read it with AI first" hint. On a normal
+ * health thread the banner is absent. Replaces the deleted drawer's not-indexed /
+ * scope coverage at the component level; the fenced-send guarantee is pinned by
+ * `coach-send-target.test.ts`.
+ *
+ * `pendingDocumentId` seeds from the `initialDocumentId` prop via a `useState`
+ * initializer, so the banner resolves in a single static-markup pass. The
+ * document detail (`/api/documents/inbound/<id>`) is seeded into the cache so the
+ * title + indexed status render without a network call.
+ */
+
+const DOC_ID = "e2edocscopedoc0000000001";
+const TITLE = "Chest X-ray report";
+
+const NOT_INDEXED_HINT =
+  "Read this document with AI first in the vault so the Coach can answer about it.";
+
+function makeClient(hasContentIndex: boolean): QueryClient {
+  const client = new QueryClient({
+    defaultOptions: { queries: { retry: false } },
+  });
+  // A fresh doc scope has no thread yet — keep the rail empty so the surface
+  // stays on the new-chat hero and the banner is the thing under test.
+  client.setQueryData(queryKeys.coachConversations(), {
+    conversations: [],
+    nextCursor: null,
+  });
+  client.setQueryData(queryKeys.coachAboutMeQuestions(), { questions: [] });
+  client.setQueryData(queryKeys.inboundDocument(DOC_ID), {
+    id: DOC_ID,
+    title: TITLE,
+    filename: "xray.pdf",
+    hasContentIndex,
+  });
+  return client;
+}
+
+function render(node: React.ReactNode, client: QueryClient): string {
+  return renderToStaticMarkup(
+    <I18nProvider initialLocale="en">
+      <QueryClientProvider client={client}>{node}</QueryClientProvider>
+    </I18nProvider>,
+  );
+}
+
+describe("<CoachConversation> doc-scope banner (R3)", () => {
+  it("shows the badge + 'Chatting about' title for an indexed document scope", () => {
+    const html = render(
+      <CoachConversation surface="page" initialDocumentId={DOC_ID} />,
+      makeClient(true),
+    );
+    expect(html).toContain('data-slot="coach-doc-scope"');
+    expect(html).toContain("Document");
+    expect(html).toContain(`Chatting about: ${TITLE}`);
+    // Indexed → no "read it first" hint.
+    expect(html).not.toContain(NOT_INDEXED_HINT);
+  });
+
+  it("shows the calm not-indexed hint when the document has no content index", () => {
+    const html = render(
+      <CoachConversation surface="page" initialDocumentId={DOC_ID} />,
+      makeClient(false),
+    );
+    expect(html).toContain('data-slot="coach-doc-scope"');
+    expect(html).toContain(NOT_INDEXED_HINT);
+  });
+
+  it("paints no banner on a normal health thread (no document scope)", () => {
+    const client = new QueryClient({
+      defaultOptions: { queries: { retry: false } },
+    });
+    client.setQueryData(queryKeys.coachConversations(), {
+      conversations: [],
+      nextCursor: null,
+    });
+    client.setQueryData(queryKeys.coachAboutMeQuestions(), { questions: [] });
+    const html = render(<CoachConversation surface="page" />, client);
+    expect(html).not.toContain('data-slot="coach-doc-scope"');
+  });
+});