Initial implementation of vault-os

Complete implementation across all 13 phases:

- vault-core: types, YAML frontmatter parsing, entity classification,
  filesystem ops, config, prompt composition, validation, search
- vault-watch: filesystem watcher with daemon write filtering, event
  classification
- vault-scheduler: cron engine, process executor, task runner with
  retry logic and concurrency limiting
- vault-api: Axum REST API (15 route modules), WebSocket with broadcast,
  AI assistant proxy, validation, templates
- Dashboard: React + TypeScript + Tailwind v4 with kanban, CodeMirror
  editor, dynamic view system, AI chat sidebar
- Nix flake with dev shell and NixOS module
- Graceful shutdown, inotify overflow recovery, tracing instrumentation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

dashboard/src/components/NotificationBanner.tsx

@@ -0,0 +1,49 @@
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { listNotifications, dismissNotification } from '../api/client';
+
+const LEVEL_STYLES: Record<string, string> = {
+  info: 'bg-accent/10 border-accent/30 text-accent',
+  warning: 'bg-warning/10 border-warning/30 text-warning',
+  error: 'bg-danger/10 border-danger/30 text-danger',
+  success: 'bg-success/10 border-success/30 text-success',
+};
+
+export function NotificationBanner() {
+  const queryClient = useQueryClient();
+  const { data: notifications } = useQuery({
+    queryKey: ['notifications'],
+    queryFn: listNotifications,
+    refetchInterval: 30000,
+  });
+
+  const dismiss = useMutation({
+    mutationFn: dismissNotification,
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['notifications'] }),
+  });
+
+  if (!notifications?.length) return null;
+
+  return (
+    <div className="space-y-2 px-6 pt-4">
+      {notifications.map((n) => (
+        <div
+          key={n.id}
+          className={`flex items-start gap-3 rounded-md border px-3 py-2 text-sm ${
+            LEVEL_STYLES[n.level || 'info'] || LEVEL_STYLES.info
+          }`}
+        >
+          <div className="flex-1">
+            <div className="font-medium">{n.title}</div>
+            {n.message && <div className="mt-0.5 text-xs opacity-80">{n.message}</div>}
+          </div>
+          <button
+            onClick={() => dismiss.mutate(n.id)}
+            className="shrink-0 text-xs opacity-60 hover:opacity-100"
+          >
+            dismiss
+          </button>
+        </div>
+      ))}
+    </div>
+  );
+}