feat(ui/alerts): Alerts sidebar section with Inbox/All/Rules/Silences/History

Adds `buildAlertsTreeNodes` to sidebar-utils and renders an Alerts section
between Applications and Starred in LayoutShell. The section uses an
accordion pattern — entering `/alerts/*` collapses apps/admin/starred and
restores their state on leave.

gitnexus_impact(LayoutContent, upstream) = LOW (0 direct callers; rendered
only by LayoutShell's provider wrapper).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/src/components/LayoutShell.tsx

@@ -21,7 +21,7 @@ import {
 } from '@cameleer/design-system';
 import type { SearchResult, SidebarTreeNode, DropdownItem, ButtonGroupItem, ExchangeStatus } from '@cameleer/design-system';
 import sidebarLogo from '@cameleer/design-system/assets/cameleer-logo.svg';
-import { Box, Settings, FileText, ChevronRight, Square, Pause, Star, X, User, Plus, EyeOff } from 'lucide-react';
+import { Box, Settings, FileText, ChevronRight, Square, Pause, Star, X, User, Plus, EyeOff, Bell } from 'lucide-react';
 import { AboutMeDialog } from './AboutMeDialog';
 import css from './LayoutShell.module.css';
 import { useQueryClient } from '@tanstack/react-query';
@@ -42,6 +42,7 @@ import { formatDuration } from '../utils/format-utils';
 import {
   buildAppTreeNodes,
   buildAdminTreeNodes,
+  buildAlertsTreeNodes,
   formatCount,
   readCollapsed,
   writeCollapsed,
@@ -278,6 +279,7 @@ const STATUS_ITEMS: ButtonGroupItem[] = [
 
 const SK_APPS = 'sidebar:section:apps';
 const SK_ADMIN = 'sidebar:section:admin';
+const SK_ALERTS = 'sidebar:section:alerts';
 const SK_COLLAPSED = 'sidebar:collapsed';
 
 /* ------------------------------------------------------------------ */
@@ -325,6 +327,7 @@ function LayoutContent() {
 
   // --- Admin search data (only fetched on admin pages) ----------------
   const isAdminPage = location.pathname.startsWith('/admin');
+  const isAlertsPage = location.pathname.startsWith('/alerts');
   const { data: adminUsers } = useUsers(isAdminPage);
   const { data: adminGroups } = useGroups(isAdminPage);
   const { data: adminRoles } = useRoles(isAdminPage);
@@ -367,8 +370,9 @@ function LayoutContent() {
   }, [setSelectedEnvRaw, navigate, location.pathname, location.search, queryClient]);
 
   // --- Section open states ------------------------------------------
-  const [appsOpen, setAppsOpen] = useState(() => isAdminPage ? false : readCollapsed(SK_APPS, true));
+  const [appsOpen, setAppsOpen] = useState(() => (isAdminPage || isAlertsPage) ? false : readCollapsed(SK_APPS, true));
   const [adminOpen, setAdminOpen] = useState(() => isAdminPage ? true : readCollapsed(SK_ADMIN, false));
+  const [alertsOpen, setAlertsOpen] = useState(() => isAlertsPage ? true : readCollapsed(SK_ALERTS, false));
   const [starredOpen, setStarredOpen] = useState(true);
 
   // Accordion: entering admin collapses apps + starred; leaving restores
@@ -388,6 +392,36 @@ function LayoutContent() {
     prevAdminRef.current = isAdminPage;
   }, [isAdminPage]); // eslint-disable-line react-hooks/exhaustive-deps
 
+  // Accordion: entering alerts collapses apps + admin + starred; leaving restores
+  const opsAlertsStateRef = useRef({ apps: appsOpen, admin: adminOpen, starred: starredOpen });
+  const prevAlertsRef = useRef(isAlertsPage);
+  useEffect(() => {
+    if (isAlertsPage && !prevAlertsRef.current) {
+      opsAlertsStateRef.current = { apps: appsOpen, admin: adminOpen, starred: starredOpen };
+      setAppsOpen(false);
+      setAdminOpen(false);
+      setStarredOpen(false);
+      setAlertsOpen(true);
+    } else if (!isAlertsPage && prevAlertsRef.current) {
+      setAppsOpen(opsAlertsStateRef.current.apps);
+      setAdminOpen(opsAlertsStateRef.current.admin);
+      setStarredOpen(opsAlertsStateRef.current.starred);
+      setAlertsOpen(false);
+    }
+    prevAlertsRef.current = isAlertsPage;
+  }, [isAlertsPage]); // eslint-disable-line react-hooks/exhaustive-deps
+
+  const toggleAlerts = useCallback(() => {
+    if (!isAlertsPage) {
+      navigate('/alerts/inbox');
+      return;
+    }
+    setAlertsOpen((prev) => {
+      writeCollapsed(SK_ALERTS, !prev);
+      return !prev;
+    });
+  }, [isAlertsPage, navigate]);
+
   const toggleApps = useCallback(() => {
     if (isAdminPage) {
       navigate('/exchanges');
@@ -469,6 +503,11 @@ function LayoutContent() {
     [capabilities?.infrastructureEndpoints],
   );
 
+  const alertsTreeNodes: SidebarTreeNode[] = useMemo(
+    () => buildAlertsTreeNodes(),
+    [],
+  );
+
   // --- Starred items ------------------------------------------------
   const starredItems = useMemo(
     () => collectStarredItems(sidebarApps, starredIds),
@@ -482,6 +521,7 @@ function LayoutContent() {
     if (!sidebarRevealPath) return;
     if (sidebarRevealPath.startsWith('/apps') && !appsOpen) setAppsOpen(true);
     if (sidebarRevealPath.startsWith('/admin') && !adminOpen) setAdminOpen(true);
+    if (sidebarRevealPath.startsWith('/alerts') && !alertsOpen) setAlertsOpen(true);
   }, [sidebarRevealPath]); // eslint-disable-line react-hooks/exhaustive-deps
 
   // Normalize path so sidebar highlights the app regardless of which tab is active.
@@ -771,6 +811,26 @@ function LayoutContent() {
         </Sidebar.Section>
       </div>
 
+      {/* Alerts section */}
+      <Sidebar.Section
+        icon={createElement(Bell, { size: 16 })}
+        label="Alerts"
+        open={alertsOpen}
+        onToggle={toggleAlerts}
+        active={isAlertsPage}
+      >
+        <SidebarTree
+          nodes={alertsTreeNodes}
+          selectedPath={location.pathname}
+          isStarred={isStarred}
+          onToggleStar={toggleStar}
+          filterQuery={filterQuery}
+          persistKey="alerts"
+          autoRevealPath={sidebarRevealPath}
+          onNavigate={handleSidebarNavigate}
+        />
+      </Sidebar.Section>
+
       {/* Starred section — only when there are starred items */}
       {starredItems.length > 0 && (
         <Sidebar.Section