fix(provenance): address #143 re-review — shared resolver + decoupled badge

Architecture & design:
- Arch A: introduce resolveProvenance() as the single source of truth for
  deriving a write's actor/aiChatId from the SIGNED identity, and wire it into
  BOTH transport seams — the REST jwt.strategy and the collab
  authentication.extension. Previously the collab seam derived actor from the
  token claim alone and ignored user.isAgent, so a flagged service account's
  page-content edits over the websocket persisted as lastUpdatedSource='user',
  drifting from REST. The seams now share one resolver and can't diverge.
- Arch B: drop AiAgentBadge's page-history coupling. The generic ui/ badge no
  longer imports historyAtoms; it exposes an onActivate callback fired after the
  deep-link, and the history row passes onActivate to close its own modal.

Suggestions/warnings:
- S1: soften the jwt.strategy provenance comment (applies to every REST write).
- S2/suggestion-3: drop the redundant comment-list-item null-aiChatId test
  (covered by ai-agent-badge.test.tsx).
- S3: de-duplicate jwt.strategy.spec test #3 (the no-claim→'user' half
  duplicated test #2); keep only the signed actor='agent' claim assertion.
- W2: add keyboard-activation tests for the badge (Enter/Space, unrelated key).
- W3: flip the design doc status to "реализовано (#143)".

Tests:
- new auth-provenance.decorator.spec.ts unit-tests resolveProvenance +
  agentSourceFields.
- new collab-seam test: is_agent user with no claim → actor='agent'
  (Arch A regression guard).

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

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

@@ -8,7 +8,6 @@ import {
   aiChatWindowOpenAtom,
   aiChatDraftAtom,
 } from "@/features/ai-chat/atoms/ai-chat-atom.ts";
-import { historyAtoms } from "@/features/page-history/atoms/history-atoms.ts";
 
 // matchMedia (read by MantineProvider) is stubbed globally in vitest.setup.ts.
 
@@ -20,6 +19,33 @@ function renderBadge(props: { authorName?: string; aiChatId?: string | null }) {
   );
 }
 
+// Render a clickable badge inside an explicit jotai store, with a leftover draft
+// and an onActivate + parent-click spy, so the deep-link side effects are
+// assertable. Returns the store and spies.
+function setupClickable() {
+  const store = createStore();
+  store.set(aiChatDraftAtom, "leftover draft from another chat");
+  const onActivate = vi.fn();
+  const onParentClick = vi.fn();
+  render(
+    <Provider store={store}>
+      <MantineProvider>
+        <div onClick={onParentClick}>
+          <AiAgentBadge authorName="Bot" aiChatId="chat-1" onActivate={onActivate} />
+        </div>
+      </MantineProvider>
+    </Provider>,
+  );
+  return { store, onActivate, onParentClick, badge: screen.getByRole("button") };
+}
+
+function expectDeepLinked(store: ReturnType<typeof createStore>, onActivate: ReturnType<typeof vi.fn>) {
+  expect(store.get(activeAiChatIdAtom)).toBe("chat-1");
+  expect(store.get(aiChatWindowOpenAtom)).toBe(true);
+  expect(store.get(aiChatDraftAtom)).toBe(""); // draft cleared
+  expect(onActivate).toHaveBeenCalledTimes(1); // caller closes its own modal etc.
+}
+
 describe("AiAgentBadge", () => {
   it("renders the AI-agent label", () => {
     renderBadge({ authorName: "Bot" });
@@ -33,33 +59,31 @@ describe("AiAgentBadge", () => {
     expect(badge.textContent).toContain("AI-agent");
   });
 
-  it("deep-links on click: sets the active chat, clears the draft, opens the AI-chat window, closes the history modal — and stops propagation", () => {
-    const store = createStore();
-    // Pre-set the state the click must change, so the assertions are meaningful.
-    store.set(historyAtoms, true); // history modal open
-    store.set(aiChatDraftAtom, "leftover draft from another chat");
-    const onParentClick = vi.fn();
-
-    render(
-      <Provider store={store}>
-        <MantineProvider>
-          {/* Parent click handler must NOT fire — the badge stops propagation. */}
-          <div onClick={onParentClick}>
-            <AiAgentBadge authorName="Bot" aiChatId="chat-1" />
-          </div>
-        </MantineProvider>
-      </Provider>,
-    );
-
-    fireEvent.click(screen.getByRole("button"));
-
-    expect(store.get(activeAiChatIdAtom)).toBe("chat-1");
-    expect(store.get(aiChatWindowOpenAtom)).toBe(true);
-    expect(store.get(aiChatDraftAtom)).toBe(""); // draft cleared
-    expect(store.get(historyAtoms)).toBe(false); // history modal closed
+  it("click deep-links: sets active chat, clears draft, opens window, fires onActivate, stops propagation", () => {
+    const { store, onActivate, onParentClick, badge } = setupClickable();
+    fireEvent.click(badge);
+    expectDeepLinked(store, onActivate);
     expect(onParentClick).not.toHaveBeenCalled(); // stopPropagation contained the click
   });
 
+  it.each(["Enter", " "])(
+    "keyboard %j activates the deep-link (same side effects as click)",
+    (key) => {
+      const { store, onActivate, badge } = setupClickable();
+      fireEvent.keyDown(badge, { key });
+      expectDeepLinked(store, onActivate);
+    },
+  );
+
+  it("an unrelated key does NOT activate the badge", () => {
+    const { store, onActivate, badge } = setupClickable();
+    fireEvent.keyDown(badge, { key: "Tab" });
+    expect(store.get(activeAiChatIdAtom)).toBeNull();
+    expect(store.get(aiChatWindowOpenAtom)).toBe(false);
+    expect(store.get(aiChatDraftAtom)).toBe("leftover draft from another chat");
+    expect(onActivate).not.toHaveBeenCalled();
+  });
+
   it.each([{ aiChatId: null }, {}])(
     "is a plain non-clickable label without a chat target (%o)",
     (props) => {

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

@@ -8,11 +8,14 @@ import {
   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;
+  // Fired after the badge deep-links into its chat. The caller handles its own
+  // context (e.g. the page-history row closes the history modal) so this generic
+  // ui/ primitive stays free of cross-feature coupling (#143 review Arch B).
+  onActivate?: () => void;
 }
 
 /**
@@ -21,18 +24,22 @@ interface AiAgentBadgeProps {
  * 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.
+ * badge deep-links into that chat: it sets the active-chat atom and opens the
+ * floating AI-chat window, then invokes `onActivate` so the caller can react
+ * (e.g. the history modal closes itself). 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) {
+export function AiAgentBadge({
+  authorName,
+  aiChatId,
+  onActivate,
+}: 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 ?? "",
@@ -47,9 +54,9 @@ export function AiAgentBadge({ authorName, aiChatId }: AiAgentBadgeProps) {
       // unsent draft so it does not leak from the previously open chat.
       setDraft("");
       setAiChatWindowOpen(true);
-      setHistoryModalOpen(false);
+      onActivate?.();
     },
-    [aiChatId, setActiveChatId, setDraft, setAiChatWindowOpen, setHistoryModalOpen],
+    [aiChatId, setActiveChatId, setDraft, setAiChatWindowOpen, onActivate],
   );
 
   const badge = (