Add "Start Workflow" button to trigger CEO agent from web UI

New endpoint POST /api/cases/{case_number}/start-workflow creates a
Paperclip issue, wakes the CEO agent via wakeup API, and transitions
case status to "processing". Button appears on case page only when
status is "new" or "documents_ready".

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web-ui/src/lib/api/cases.ts

@@ -167,6 +167,32 @@ export function useGitStatus(caseNumber: string | undefined) {
   });
 }
 
+export type StartWorkflowResult = {
+  case_number: string;
+  status: string;
+  issue_id: string;
+  issue_identifier: string;
+  project_url: string;
+  wakeup: Record<string, unknown>;
+};
+
+export function useStartWorkflow(caseNumber: string | undefined) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: () =>
+      apiRequest<StartWorkflowResult>(
+        `/api/cases/${caseNumber}/start-workflow`,
+        { method: "POST" },
+      ),
+    onSuccess: () => {
+      qc.invalidateQueries({ queryKey: casesKeys.all });
+      if (caseNumber) {
+        qc.invalidateQueries({ queryKey: casesKeys.detail(caseNumber) });
+      }
+    },
+  });
+}
+
 export function useWorkflowStatus(caseNumber: string | undefined) {
   return useQuery({
     queryKey: [...casesKeys.all, "workflow", caseNumber ?? ""] as const,