M-029 Pass 1 batch 1: migrate 4 single-mutation pages to useTrackedMutation

Drains the Bundle 8 useMutation backlog (56 -> 52). Each migration declares

explicit invalidates per the M-009 contract; the wrapper invalidates BEFORE

calling the caller's onSuccess so user code drops the redundant qc.invalidateQueries.

Pages migrated:

  - AgentsPage.tsx        invalidates: [['agents'], ['agents', 'retired']]

  - CertificatesPage.tsx  invalidates: [['certificates']]

  - DigestPage.tsx        invalidates: 'noop' (sendDigest is a server-side email

                            dispatch — no client query reflects digest-send state)

  - IssuerDetailPage.tsx  invalidates: [['issuer', id]] (testIssuerConnection

                            updates last_tested_at server-side)

Verification:

  legacy useMutation count   56 -> 52 (-4 sites)

  useTrackedMutation count    0 ->  4 (+4 sites)

  invalidation surface      82 -> 84 (+2; DigestPage is noop, AgentsPage

                                  collapses 2 invalidates into 1 array, others +1)

Closes 4 of 56 sites toward M-029 Pass 1 completion.

web/src/pages/IssuerDetailPage.tsx

@@ -1,5 +1,6 @@
 import { useParams, useNavigate } from 'react-router-dom';
-import { useQuery, useMutation } from '@tanstack/react-query';
+import { useQuery } from '@tanstack/react-query';
+import { useTrackedMutation } from '../hooks/useTrackedMutation';
 import { getIssuer, testIssuerConnection, getCertificates } from '../api/client';
 import PageHeader from '../components/PageHeader';
 import StatusBadge from '../components/StatusBadge';
@@ -46,9 +47,9 @@ export default function IssuerDetailPage() {
     enabled: !!id,
   });
 
-  const testMutation = useMutation({
+  const testMutation = useTrackedMutation({
     mutationFn: () => testIssuerConnection(id!),
-    onSuccess: () => refetch(),
+    invalidates: [['issuer', id]],
   });
 
   if (error) {