feat(comments): attribute MCP agent comments as AI (unspoofable provenance)

Mark comments (and, via existing page provenance, pages) created under an
is_agent service account as authored by AI, derived from the SIGNED server
identity rather than any client field, and render the existing AI badge in
the comments sidebar.

Backend (B1):
- Add additive users.is_agent boolean (default false) migration; reflect in
  the Users Kysely type, the user repo baseFields, and (via Selectable) the
  User entity.
- jwt.strategy: derive req.raw.actor from user.isAgent (an is_agent account
  stamps every write 'agent'); external MCP has no internal ai_chats row so
  aiChatId stays null. Non-spoofable: a plain user cannot obtain
  created_source='agent'.
- Loosen the provenance aiChatId type to string|null across token.service and
  the JwtPayload/JwtCollabPayload claims (type-level only; the internal AI-chat
  path still passes a real aiChatId).

Frontend (B2):
- Extend IComment with createdSource/aiChatId/resolvedSource (backend already
  returns them via selectAll).
- Extract the local AiAgentBadge from history-item into a shared
  components/ui/ai-agent-badge.tsx (clickable deep-link when aiChatId present,
  plain label when null/absent); reuse it in history-item and render it in
  comment-list-item next to the author name when createdSource==='agent'.

Tests: comment.service agent/null-aiChatId provenance, jwt.strategy provenance
derivation + anti-spoof, AiAgentBadge clickable/non-clickable branches, and
comment-list-item badge render/no-render.

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

apps/client/src/components/ui/ai-agent-badge.test.tsx

@@ -0,0 +1,60 @@
+import { describe, it, expect, vi, beforeAll } from "vitest";
+import { render, screen, fireEvent } from "@testing-library/react";
+import { MantineProvider } from "@mantine/core";
+import { AiAgentBadge } from "./ai-agent-badge";
+
+// MantineProvider reads window.matchMedia (color scheme) on mount, which jsdom
+// does not implement. Provide a minimal stub so the provider can render.
+beforeAll(() => {
+  Object.defineProperty(window, "matchMedia", {
+    writable: true,
+    value: (query: string) => ({
+      matches: false,
+      media: query,
+      onchange: null,
+      addListener: vi.fn(),
+      removeListener: vi.fn(),
+      addEventListener: vi.fn(),
+      removeEventListener: vi.fn(),
+      dispatchEvent: vi.fn(),
+    }),
+  });
+});
+
+function renderBadge(props: { authorName?: string; aiChatId?: string | null }) {
+  return render(
+    <MantineProvider>
+      <AiAgentBadge {...props} />
+    </MantineProvider>,
+  );
+}
+
+describe("AiAgentBadge", () => {
+  it("renders the AI-agent label", () => {
+    renderBadge({ authorName: "Bot" });
+    expect(screen.getByText("AI-agent")).toBeDefined();
+  });
+
+  it("is clickable (accessible button) when aiChatId is present", () => {
+    renderBadge({ authorName: "Bot", aiChatId: "chat-1" });
+    const badge = screen.getByRole("button");
+    expect(badge).toBeDefined();
+    expect(badge.textContent).toContain("AI-agent");
+    // Clicking does not throw — the deep-link handler runs against the default
+    // jotai store. (Asserting the badge exposes an interactive role is the
+    // observable contract; the atom side-effects are covered by the history UI.)
+    fireEvent.click(badge);
+  });
+
+  it("is a plain non-clickable label when aiChatId is null (external MCP agent)", () => {
+    renderBadge({ authorName: "Bot", aiChatId: null });
+    expect(screen.getByText("AI-agent")).toBeDefined();
+    // No interactive role is exposed when there is no chat to deep-link into.
+    expect(screen.queryByRole("button")).toBeNull();
+  });
+
+  it("is non-clickable when aiChatId is absent", () => {
+    renderBadge({ authorName: "Bot" });
+    expect(screen.queryByRole("button")).toBeNull();
+  });
+});

apps/client/src/components/ui/ai-agent-badge.tsx

@@ -0,0 +1,92 @@
+import { Badge, Tooltip } from "@mantine/core";
+import { IconSparkles } from "@tabler/icons-react";
+import { useCallback } from "react";
+import { useTranslation } from "react-i18next";
+import { useSetAtom } from "jotai";
+import {
+  activeAiChatIdAtom,
+  aiChatWindowOpenAtom,
+  aiChatDraftAtom,
+} from "@/features/ai-chat/atoms/ai-chat-atom.ts";
+import { historyAtoms } from "@/features/page-history/atoms/history-atoms.ts";
+
+interface AiAgentBadgeProps {
+  authorName?: string;
+  aiChatId?: string | null;
+}
+
+/**
+ * Badge marking content written by the AI agent (provenance C3 / §7.4). It is
+ * ADDITIVE — shown next to the human author, never replacing them. Reused by the
+ * page-history list and the comments sidebar.
+ *
+ * When the item carries an `aiChatId` (an internal AI-chat edit), clicking the
+ * badge deep-links into that chat: it sets the active-chat atom, opens the
+ * floating AI-chat window, and closes the history modal. When `aiChatId` is
+ * null/absent (an external MCP write with no internal ai_chats row), the badge
+ * is a plain non-clickable label. The click is contained (stopPropagation) so it
+ * does not also trigger an enclosing row's click handler.
+ */
+export function AiAgentBadge({ authorName, aiChatId }: AiAgentBadgeProps) {
+  const { t } = useTranslation();
+  const setAiChatWindowOpen = useSetAtom(aiChatWindowOpenAtom);
+  const setActiveChatId = useSetAtom(activeAiChatIdAtom);
+  const setDraft = useSetAtom(aiChatDraftAtom);
+  const setHistoryModalOpen = useSetAtom(historyAtoms);
+
+  const tooltip = t("Edited by AI agent on behalf of {{name}}", {
+    name: authorName ?? "",
+  });
+
+  const openChat = useCallback(
+    (event: React.SyntheticEvent) => {
+      event.stopPropagation();
+      if (!aiChatId) return;
+      setActiveChatId(aiChatId);
+      // Switching to another chat must start with a clean composer — clear any
+      // unsent draft so it does not leak from the previously open chat.
+      setDraft("");
+      setAiChatWindowOpen(true);
+      setHistoryModalOpen(false);
+    },
+    [aiChatId, setActiveChatId, setDraft, setAiChatWindowOpen, setHistoryModalOpen],
+  );
+
+  const badge = (
+    <Badge
+      size="sm"
+      variant="light"
+      color="violet"
+      radius="sm"
+      leftSection={<IconSparkles size={12} stroke={2} />}
+      style={aiChatId ? { cursor: "pointer" } : undefined}
+      {...(aiChatId
+        ? {
+            // Keep the default Badge root element (not a <button>) to avoid an
+            // invalid <button>-in-<button> nesting inside a row's
+            // UnstyledButton; expose it as an accessible button via
+            // role/keyboard.
+            role: "button",
+            tabIndex: 0,
+            onClick: openChat,
+            onKeyDown: (event: React.KeyboardEvent) => {
+              if (event.key === "Enter" || event.key === " ") {
+                event.preventDefault();
+                openChat(event);
+              }
+            },
+          }
+        : {})}
+    >
+      {t("AI-agent")}
+    </Badge>
+  );
+
+  return (
+    <Tooltip label={tooltip} withArrow>
+      {badge}
+    </Tooltip>
+  );
+}
+
+export default AiAgentBadge;