Strip explanatory subtitles from primary page headers

Dashboard, Infrastructure, and Storage carried descriptive blurbs under
their titles ("Monitor fleet health...", "Inspect discovered systems...",
"Track capacity..."). They read like onboarding copy, not header text on
a working monitoring tool. Removed.

PageHeader.description is already optional; the three surfaces now render
with just the title.

Refs #1429 RC2 feedback tone

frontend-modern/src/components/Storage/Storage.tsx

@@ -74,10 +74,7 @@ const Storage: Component = () => {
       class="space-y-4"
       data-testid="storage-page"
     >
-      <PageHeader
-        title="Storage"
-        description="Track capacity, cluster health, and storage alerts across local and distributed systems."
-      />
+      <PageHeader title="Storage" />
 
       <StickySummarySection desktopOnly={false}>
         <StoragePageSummary

frontend-modern/src/features/infrastructure/InfrastructurePageSurface.tsx

@@ -87,10 +87,7 @@ export function InfrastructurePageSurface() {
       data-testid="infrastructure-page"
       class="space-y-4"
     >
-      <PageHeader
-        title="Infrastructure"
-        description="Inspect discovered systems, cluster health, and resource status across the monitored estate."
-      />
+      <PageHeader title="Infrastructure" />
 
       <Show
         when={!loading() || initialLoadComplete()}

frontend-modern/src/pages/Dashboard.tsx

@@ -169,10 +169,7 @@ export default function Dashboard() {
 
   return (
     <main data-testid="dashboard-page" class="space-y-6">
-      <PageHeader
-        title="Dashboard"
-        description="Monitor fleet health, recent alerts, storage pressure, and recovery readiness from one surface."
-      />
+      <PageHeader title="Dashboard" />
 
       {/* Connection warning banner — shown above all content, NOT a full-page takeover */}
       <Show when={hasConnectionError() && initialLoadComplete()}>