feat(frontend): c2 config card + execute modal (sprint 8 phase 1)

- frontend/src/api/c2.ts: 6 typed API calls (getC2Config, putC2Config,
  deleteC2Config, testC2Config, listCallbacks, executeC2) following the
  frozen M1+M2 backend contracts
- frontend/src/api/types.ts: C2Config, C2ConfigInput, C2TestResult,
  C2Callback, C2CallbacksResponse, C2Task, C2ExecuteInput, C2ExecuteResponse
- frontend/src/hooks/useC2.ts: useC2Config, useUpdateC2Config,
  useDeleteC2Config, useTestC2Config, useC2Callbacks, useExecuteC2
- frontend/src/components/C2ConfigCard.tsx: engagement-scoped C2 config
  card (url + write-only token + verify-tls + save/delete/test-connection),
  503 disabled state, ConfirmDialog on delete
- frontend/src/components/ExecuteViaC2Modal.tsx: callback picker table
  (mono data cells), commands textarea pre-filled from rt.commands,
  Launch disabled until row selected + non-empty commands
- frontend/src/pages/EngagementFormPage.tsx: embed C2ConfigCard in edit
  mode only, admin+redteam only (canEditEngagements gate)
- frontend/src/pages/SimulationFormPage.tsx: Execute via C2 button in RT
  card, visible only when !isDone && canEditRT && hasC2Config; opens modal
- Tests: 33 new tests across api/c2, components/C2ConfigCard,
  components/ExecuteViaC2Modal, EngagementFormPage, SimulationFormPage
  (172 total, 139 baseline + 33 new, all passing)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/SimulationFormPage.tsx

@@ -12,12 +12,14 @@ import {
   useTransitionSimulation,
   useUpdateSimulation,
 } from '@/hooks/useSimulations';
+import { useC2Config } from '@/hooks/useC2';
 import { FormField, TextArea, TextInput } from '@/components/FormField';
 import { LoadingState } from '@/components/LoadingState';
 import { ErrorState } from '@/components/ErrorState';
 import { SimulationStatusBadge } from '@/components/SimulationStatusBadge';
 import { ConfirmDialog } from '@/components/ConfirmDialog';
 import { MitreTechniquesField } from '@/components/MitreTechniquesField';
+import { ExecuteViaC2Modal } from '@/components/ExecuteViaC2Modal';
 
 interface RedteamFormState {
   name: string;
@@ -61,6 +63,13 @@ export function SimulationFormPage(): JSX.Element {
   const { push } = useToast();
   const { isAdmin, isRedteam, isSoc, canEditEngagements } = useAuth();
 
+  const canEditRT = isAdmin || isRedteam;
+  const c2ConfigQuery = useC2Config(
+    !isNew && typeof engagementId === 'number' ? engagementId : undefined,
+    { enabled: !isNew && canEditRT },
+  );
+  const hasC2Config = c2ConfigQuery.data !== null && c2ConfigQuery.data !== undefined;
+
   const detail = useSimulation(isNew ? undefined : simulationId);
   const createMutation = useCreateSimulation(engagementId ?? 0);
   const updateMutation = useUpdateSimulation(simulationId ?? 0, engagementId ?? 0);
@@ -72,6 +81,7 @@ export function SimulationFormPage(): JSX.Element {
   const [nameError, setNameError] = useState<string | null>(null);
   const [submitError, setSubmitError] = useState<string | null>(null);
   const [showDeleteConfirm, setShowDeleteConfirm] = useState(false);
+  const [showC2Modal, setShowC2Modal] = useState(false);
 
   useEffect(() => {
     if (!isNew && detail.data) {
@@ -109,7 +119,6 @@ export function SimulationFormPage(): JSX.Element {
   // US-18: Done = fully read-only, Reopen only
   const isDone = status === 'done';
 
-  const canEditRT = isAdmin || isRedteam;
   const socCanEdit = isSoc && (status === 'review_required' || status === 'done');
   const socBlocked = isSoc && (status === 'pending' || status === 'in_progress');
 
@@ -383,6 +392,19 @@ export function SimulationFormPage(): JSX.Element {
               rows={5}
             />
           </FormField>
+
+          {!isDone && canEditRT && hasC2Config && (
+            <div className="pt-xs">
+              <button
+                type="button"
+                data-testid="c2-execute-btn"
+                className="btn-outline"
+                onClick={() => setShowC2Modal(true)}
+              >
+                Execute via C2
+              </button>
+            </div>
+          )}
         </form>
 
         {/* SOC card */}
@@ -512,6 +534,15 @@ export function SimulationFormPage(): JSX.Element {
           onCancel={() => setShowDeleteConfirm(false)}
         />
       )}
+
+      {showC2Modal && simulationId && typeof engagementId === 'number' && (
+        <ExecuteViaC2Modal
+          simulationId={simulationId}
+          engagementId={engagementId}
+          initialCommands={rt.commands}
+          onClose={() => setShowC2Modal(false)}
+        />
+      )}
     </div>
   );
 }