docs: add Sub-Dokumentation section to AGENTS.md and CLAUDE.md for improved documentation structure

- Introduced a new section detailing the Single Source of Truth for various components, linking to their respective CLAUDE.md files.
- Enhanced clarity on documentation organization across different areas of the project.

AGENTS.md

@@ -3,3 +3,18 @@
 
 This version has breaking changes — APIs, conventions, and file structure may all differ from your training data. Read the relevant guide in `node_modules/next/dist/docs/` before writing any code. Heed deprecation notices.
 <!-- END:nextjs-agent-rules -->
+
+## Sub-Dokumentation
+
+Jeder Ordner hat eine eigene CLAUDE.md als Single Source of Truth. Vor Änderungen immer das zugehörige Dok lesen.
+
+| Bereich | Dok |
+|---------|-----|
+| Convex Backend | [convex/CLAUDE.md](convex/CLAUDE.md) |
+| Canvas-Engine | [components/canvas/CLAUDE.md](components/canvas/CLAUDE.md) |
+| Design System (ShadCN) | [components/ui/CLAUDE.md](components/ui/CLAUDE.md) |
+| Billing & Credits UI | [components/billing/CLAUDE.md](components/billing/CLAUDE.md) |
+| Dashboard | [components/dashboard/CLAUDE.md](components/dashboard/CLAUDE.md) |
+| Next.js Routing | [app/CLAUDE.md](app/CLAUDE.md) |
+| Utilities & Shared Logic | [lib/CLAUDE.md](lib/CLAUDE.md) |
+| Custom Hooks | [hooks/CLAUDE.md](hooks/CLAUDE.md) |