feat(orchestrator): authoritative failure-count badge endpoint (DEBT-042)

New GET /api/v1/orchestrator/events/stats?since=1h&success=false&kind=...
backed by repo.count_orchestrator_failures(since_ts, kind), which
counts failed rows across both orchestrator_events and
orchestrator_emails since the cutoff.

Window parser accepts ^\d+[smhd]$, capped at 7d. Today only
success=false is accepted on this surface so the endpoint isn't
accidentally repurposed before the next consumer is properly
designed.

Orchestrator.tsx polls the endpoint on mount + every 30 s and
renders the authoritative DB-derived count instead of deriving from
the in-memory SSE buffer + one paginated page (which silently
excluded failures older than the local window).

decnet_web/src/components/Orchestrator.test.tsx

@@ -26,6 +26,26 @@ vi.mock('./useOrchestratorStream', () => ({
 import api from '../utils/api';
 const apiGet = api.get as ReturnType<typeof vi.fn>;
 
+/** Two endpoints fire at mount — events list + failure-count stats.
+ *  This dispatcher maps URLs to canned responses so per-test cases stay
+ *  focused on the path they care about. */
+const buildApiResponder = (overrides: {
+  events?: { data: unknown[]; total: number };
+  failures?: number;
+} = {}) => {
+  const events = overrides.events ?? { data: [], total: 0 };
+  const failures = overrides.failures ?? 0;
+  return (url: string) => {
+    if (url.startsWith('/orchestrator/events/stats')) {
+      return Promise.resolve({ data: { count: failures } });
+    }
+    if (url.startsWith('/orchestrator/events')) {
+      return Promise.resolve({ data: events });
+    }
+    return Promise.resolve({ data: {} });
+  };
+};
+
 const renderPage = () =>
   render(
     <MemoryRouter initialEntries={['/orchestrator']}>
@@ -40,7 +60,7 @@ describe('Orchestrator', () => {
   });
 
   it('renders the empty state when the API returns no events', async () => {
-    apiGet.mockResolvedValueOnce({ data: { data: [], total: 0 } });
+    apiGet.mockImplementation(buildApiResponder());
 
     renderPage();
 
@@ -50,11 +70,14 @@ describe('Orchestrator', () => {
   });
 
   it('switches the kind filter and refetches scoped to that kind', async () => {
-    apiGet.mockResolvedValue({ data: { data: [], total: 0 } });
+    apiGet.mockImplementation(buildApiResponder());
 
     renderPage();
-    await waitFor(() => expect(apiGet).toHaveBeenCalledTimes(1));
-    expect(apiGet.mock.calls[0][0]).toMatch(/^\/orchestrator\/events\?limit=50&offset=0$/);
+    await waitFor(() =>
+      expect(
+        apiGet.mock.calls.some((c) => /^\/orchestrator\/events\?limit=50&offset=0$/.test(c[0])),
+      ).toBe(true),
+    );
 
     await userEvent.click(screen.getByRole('tab', { name: /^email$/ }));
 
@@ -65,7 +88,7 @@ describe('Orchestrator', () => {
   });
 
   it('prepends a row when the live stream pushes a traffic event', async () => {
-    apiGet.mockResolvedValueOnce({ data: { data: [], total: 0 } });
+    apiGet.mockImplementation(buildApiResponder());
 
     renderPage();
     await waitFor(() => expect(capturedOnEvent).not.toBeNull());
@@ -90,4 +113,31 @@ describe('Orchestrator', () => {
     // 1 event shown after a single push.
     expect(screen.getByText(/1 EVENTS SHOWN/i)).toBeInTheDocument();
   });
+
+  it('renders the failure-count badge from the stats endpoint (DEBT-042)', async () => {
+    apiGet.mockImplementation(buildApiResponder({ failures: 42 }));
+
+    renderPage();
+
+    expect(await screen.findByText(/42 FAILURES \/ 1H/i)).toBeInTheDocument();
+    // Stats endpoint is the authoritative source — verify it was actually queried.
+    expect(
+      apiGet.mock.calls.some((c) =>
+        /\/orchestrator\/events\/stats\?since=1h&success=false/.test(c[0]),
+      ),
+    ).toBe(true);
+  });
+
+  it('hides the failure-count badge when the stats endpoint reports zero', async () => {
+    apiGet.mockImplementation(buildApiResponder({ failures: 0 }));
+
+    renderPage();
+    await waitFor(() =>
+      expect(
+        apiGet.mock.calls.some((c) => /\/orchestrator\/events\/stats/.test(c[0])),
+      ).toBe(true),
+    );
+
+    expect(screen.queryByText(/FAILURES \/ 1H/i)).not.toBeInTheDocument();
+  });
 });

decnet_web/src/components/Orchestrator.tsx

@@ -36,7 +36,6 @@ type KindFilter = 'all' | 'traffic' | 'file' | 'email';
 type StreamStatus = 'connecting' | 'live' | 'error';
 
 const ROW_CAP = 500;
-const HOUR_MS = 60 * 60 * 1000;
 const FRESH_MS = 5_000;
 
 const timeAgo = (dateStr: string | null): string => {
@@ -64,6 +63,7 @@ const Orchestrator: React.FC = () => {
   const [paused, setPaused] = useState(false);
   const [now, setNow] = useState(Date.now());
   const [selected, setSelected] = useState<OrchestratorEntry | null>(null);
+  const [failuresLastHour, setFailuresLastHour] = useState(0);
 
   const limit = 50;
   const pausedRef = useRef(paused);
@@ -75,6 +75,27 @@ const Orchestrator: React.FC = () => {
     return () => clearInterval(t);
   }, []);
 
+  // Authoritative failure count from the DB — see DEBT-042. The
+  // in-memory derivation it replaced was bounded by the SSE buffer +
+  // one paginated page, so failures older than the local window were
+  // silently excluded and the badge read low on busy fleets.
+  useEffect(() => {
+    let cancelled = false;
+    const fetchStats = async () => {
+      try {
+        const res = await api.get(
+          '/orchestrator/events/stats?since=1h&success=false',
+        );
+        if (!cancelled) setFailuresLastHour(res.data?.count ?? 0);
+      } catch {
+        // Silent: the badge is a hint, missing data shouldn't blow up the page.
+      }
+    };
+    fetchStats();
+    const t = setInterval(fetchStats, 30_000);
+    return () => { cancelled = true; clearInterval(t); };
+  }, []);
+
   const fetchEvents = async () => {
     setLoading(true);
     try {
@@ -163,13 +184,6 @@ const Orchestrator: React.FC = () => {
     return merged.filter((r) => r.kind === kindParam);
   }, [streamRows, rows, kindParam]);
 
-  const failuresLastHour = useMemo(() => {
-    const cutoff = now - HOUR_MS;
-    return [...streamRows, ...rows].filter(
-      (r) => !r.success && new Date(r.ts).getTime() >= cutoff,
-    ).length;
-  }, [streamRows, rows, now]);
-
   const statusLabel =
     status === 'live' ? 'LIVE'
       : status === 'connecting' ? 'CONNECTING'