feat: hierarchical notebook system - trash, selectors, breadcrumb, sidebar tree

- Schema: soft delete with trashedAt on Notebook model
- API: PATCH/GET notebooks support trashedAt filtering with cascade
- Sidebar: recursive tree rendering with collapse/expand, visual guides, hover actions
- HierarchicalNotebookSelector: portal-based dropdown with search, breadcrumbs, dropUp support
- AI chat: context selector with Toutes mes notes + notebook selector
- Agent detail: flat selects replaced with HierarchicalNotebookSelector
- Breadcrumb: notebook path display on home page
- Trash view: card grid with countdown, restore/permanent delete
- CSS: design tokens (ink, paper, blueprint, concrete, etc.)
- Types: parentId, trashedAt added to Notebook interface

memento-note/app/(main)/agents/page.tsx

@@ -13,8 +13,9 @@ export default async function AgentsPage() {
   const [agents, notebooks] = await Promise.all([
     getAgents(),
     prisma.notebook.findMany({
-      where: { userId },
-      orderBy: { order: 'asc' }
+      where: { userId, trashedAt: null },
+      orderBy: { order: 'asc' },
+      select: { id: true, name: true, icon: true, parentId: true, trashedAt: true }
     })
   ])