feat(ui): fold the Workflows page into Dashboard → Analytics → Workflow

The workflow analytics now render under the Analytics tab's Workflow
sub-tab; ?tab= and ?sub= deep-link the Dashboard, /workflows redirects there,
and the sidebar drops its Workflows item.

client/src/pages/Workflows.tsx

@@ -1,6 +1,7 @@
 /**
  * @file Workflows.tsx
- * @description Workflows page. Opens on this dashboard's OWN pipelines — per-node
+ * @description The workflow analytics, shown inside Dashboard → Analytics → Workflow (the
+ * old `/workflows` route redirects there). Opens on this dashboard's OWN pipelines — per-node
  * pass rates across every lane, and which skills/plugins actually get used — then
  * the Claude Code orchestration analytics: headline stats, Workflow-tool runs, the
  * spawning DAG, error propagation, session complexity, compaction impact and the
@@ -494,7 +495,7 @@ function PageHeader({
         </div>
         <div>
           <div className="flex items-center gap-2">
-            <h1 className="text-lg font-semibold text-fg-primary">{t("title")}</h1>
+            <h2 className="text-lg font-semibold text-fg-primary">{t("title")}</h2>
             {wsConnected ? (
               <span className="flex items-center gap-1.5 text-[11px] text-status-success bg-status-success/10 border border-status-success/20 px-2 py-0.5 rounded-full">
                 <span className="w-1.5 h-1.5 rounded-full bg-status-success animate-pulse-dot" />