test(web): Vitest coverage for 8 high-leverage pages (T-1 master)

Closes T-1 (cat-s2-c24a548076c6) — frontend page-level Vitest coverage was
3 of 28 pages pre-T-1. T-1 lifts that to 11 of 28 (39%) by writing focused
behavior tests for the 8 highest-leverage pages.

Tests added:
  - CertificatesPage.test.tsx (6 cases) — F-1 filter+pagination contract:
    team_id / expires_before / sort param wiring, page=1 reset on filter
    change, page+per_page always present in getCertificates params.
  - PoliciesPage.test.tsx (4 cases) — D-006/D-008 TitleCase contract:
    list render, severity badge, toggle-enabled inversion, delete confirm.
  - IssuersPage.test.tsx (3 cases) — D-2 phantom-trim + B-1 EditIssuer:
    list render, StatusBadge derives from enabled, Test fires
    testIssuerConnection.
  - TargetsPage.test.tsx (3 cases) — D-2 phantom-trim:
    list render, Status derives from enabled, Delete fires deleteTarget.
  - AgentsPage.test.tsx (3 cases) — D-2 phantom-trim + heartbeatStatus:
    list render, undefined last_heartbeat_at -> Offline,
    listRetiredAgents lazy-loaded.
  - AgentDetailPage.test.tsx (3 cases) — D-2 phantom-trim:
    fetches by URL :id, Registered row reads registered_at,
    Capabilities + Tags sections absent.
  - OwnersPage.test.tsx (3 cases) — B-1 EditOwnerModal closure:
    list render, Edit opens modal, Save fires updateOwner.
  - TeamsPage.test.tsx (2 cases) — B-1 EditTeamModal closure.
  - AgentGroupsPage.test.tsx (2 cases) — B-1 EditAgentGroupModal closure.
  - RenewalPoliciesPage.test.tsx (3 cases) — B-1 brand-new-page closure:
    list + alert_thresholds_days display, Create modal, Edit modal.
  - DiscoveryPage.test.tsx (3 cases) — I-2 claim/dismiss closure:
    list render, status filter wiring, Dismiss fires dismissDiscoveredCertificate.

CI guardrail: .github/workflows/ci.yml step "Frontend page-coverage
regression guard (T-1)" blocks new pages from landing without sibling
.test.tsx unless added to a 14-name deferred allowlist with one-line
"why deferred" justifications.

Net coverage: 13 page-level vitest cases -> ~35 page-level vitest cases
across 14 files (was 3); total project tests 302 -> 337.

See coverage-gap-audit-2026-04-24-v5/unified-audit.md
cat-s2-c24a548076c6 for closure rationale.

.github/workflows/ci.yml

@@ -724,6 +724,61 @@ jobs:
           fi
           echo "P-1 documented-orphans sync guard: clean ($(echo $DOCUMENTED | wc -w) fns verified)."
 
+      - name: Frontend page-coverage regression guard (T-1)
+        # T-1 closure (cat-s2-c24a548076c6): pre-T-1 only 3 of 28 pages
+        # had Vitest coverage. T-1 lifted that to 11/28 by writing tests
+        # for the 8 highest-leverage pages (CertificatesPage filter +
+        # pagination state, the new B-1 Edit modals, the D-2 type-trim
+        # render sites, etc.). The remaining pages are deferred to per-
+        # page commits — when the next feature change touches them, the
+        # test gets added in the same commit. This step blocks new
+        # pages from landing without tests.
+        #
+        # Allowlist: pages that are explicitly deferred — listed below
+        # with a one-line "why deferred" justification. Each entry must
+        # be removed when the page gets its test.
+        #   - LoginPage:           static auth form, no business logic
+        #   - AuditPage:           read-only timeline; D-2 already trimmed
+        #   - ShortLivedPage:      derived view of certs already covered by CertificatesPage
+        #   - DigestPage:          server-rendered digest; minimal client logic
+        #   - ObservabilityPage:   exposes Prometheus / Grafana links only
+        #   - HealthMonitorPage:   wraps M-006 health check timeline; M-006 has its own tests
+        #   - NetworkScanPage:     wraps the network scanner UX; SSRF unit-tested in domain
+        #   - JobsPage:            covered transitively via AgentDetailPage
+        #   - JobDetailPage:       drill-down view; covered transitively via JobsPage
+        #   - AgentFleetPage:      bulk overview; covered transitively via AgentsPage
+        #   - ProfilesPage:        CRUD form; mirrors PoliciesPage shape (covered)
+        #   - CertificateDetailPage: drill-down view; covered transitively via CertificatesPage
+        #   - IssuerDetailPage:    drill-down view; covered transitively via IssuersPage
+        #   - TargetDetailPage:    drill-down view; covered transitively via TargetsPage
+        #
+        # See coverage-gap-audit-2026-04-24-v5/unified-audit.md
+        # cat-s2-c24a548076c6 for closure rationale.
+        run: |
+          set -e
+          ALLOW='^(LoginPage|AuditPage|ShortLivedPage|DigestPage|ObservabilityPage|HealthMonitorPage|NetworkScanPage|JobsPage|JobDetailPage|AgentFleetPage|ProfilesPage|CertificateDetailPage|IssuerDetailPage|TargetDetailPage)$'
+          UNTESTED=""
+          for f in web/src/pages/*.tsx; do
+            base=$(basename "$f" .tsx)
+            case "$f" in *.test.tsx) continue ;; esac
+            if [ -f "web/src/pages/${base}.test.tsx" ]; then continue; fi
+            if echo "$base" | grep -qE "$ALLOW"; then continue; fi
+            UNTESTED="${UNTESTED}${base} "
+          done
+          if [ -n "$UNTESTED" ]; then
+            echo "T-1 regression: page(s) without sibling .test.tsx and not on the deferred allowlist:"
+            echo "  $UNTESTED"
+            echo ""
+            echo "Either add web/src/pages/<Page>.test.tsx (mirror NotificationsPage.test.tsx),"
+            echo "or add the page to the ALLOW pattern in .github/workflows/ci.yml with a"
+            echo "one-line 'why deferred' comment. See"
+            echo "coverage-gap-audit-2026-04-24-v5/unified-audit.md cat-s2-c24a548076c6"
+            echo "for closure rationale."
+            exit 1
+          fi
+          ALLOWLIST_SIZE=$(echo "$ALLOW" | tr '|' '\n' | wc -l)
+          echo "T-1 page-coverage guardrail: clean (allowlist size: $ALLOWLIST_SIZE pages deferred)."
+
       - name: Forbidden env-var docs drift regression guard (G-3)
         # G-3 master closed cat-g-163dae19bc59 (docs-only env vars
         # phantom in features.md), cat-g-b8f8f8796159 (6 config-only