Phase 3b: Case Detail view with workflow timeline

New dynamic route /cases/[caseNumber] wired to the FastAPI details
endpoint, using Next 16's async params pattern with React's use()
hook. TanStack Query handles 5s refetchInterval so the page
self-updates during long-running processing without manual polling.

New components: CaseHeader (breadcrumb + meta), WorkflowTimeline
(5-phase RTL pipeline view), DocumentsPanel (categorized list).
Tabs split overview/documents/actions.

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

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

@@ -74,10 +74,34 @@ export function useCase(caseNumber: string | undefined) {
   return useQuery({
     queryKey: casesKeys.detail(caseNumber ?? ""),
     queryFn: ({ signal }) =>
-      apiRequest<CaseDetail>(`/api/cases/${caseNumber}`, { signal }),
+      apiRequest<CaseDetail>(`/api/cases/${caseNumber}/details`, { signal }),
     enabled: Boolean(caseNumber),
     /* Replaces the old 5s polling from vanilla index.html */
     staleTime: 5_000,
     refetchInterval: 5_000,
   });
 }
+
+export type WorkflowStatus = {
+  case_number?: string;
+  status?: CaseStatus | string;
+  current_step?: string;
+  steps?: Array<{
+    key: string;
+    label?: string;
+    status: "done" | "current" | "pending" | string;
+  }>;
+  /* FastAPI returns free-form JSON; keep it permissive */
+  [key: string]: unknown;
+};
+
+export function useWorkflowStatus(caseNumber: string | undefined) {
+  return useQuery({
+    queryKey: [...casesKeys.all, "workflow", caseNumber ?? ""] as const,
+    queryFn: ({ signal }) =>
+      apiRequest<WorkflowStatus>(`/api/cases/${caseNumber}/status`, { signal }),
+    enabled: Boolean(caseNumber),
+    staleTime: 5_000,
+    refetchInterval: 5_000,
+  });
+}