refactor: replace n8n package with overlay override

docs/packages/README.md

@@ -21,7 +21,6 @@ These packages are built from source in `pkgs/<name>/`:
 | `launch-webapp` | Launch web applications | Shell | `pkgs/launch-webapp/` |
 | `mem0` | AI memory assistant with vector storage | Python | `pkgs/mem0/` |
 | `msty-studio` | Msty Studio application | Python | `pkgs/msty-studio/` |
-| `n8n` | Workflow automation tool | Node.js | `pkgs/n8n/` |
 | `openshell` | AI shell assistant | Go | `pkgs/openshell/` |
 | `openwork` | Open-source Claude Cowork alternative powered by opencode | AppImage | `pkgs/openwork/` |
 | `pomodoro-timer` | Pomodoro timer utility | Shell | `pkgs/pomodoro-timer/` |
@@ -31,6 +30,14 @@ These packages are built from source in `pkgs/<name>/`:
 | `vibetyper` | Typing practice tool | Python | `pkgs/vibetyper/` |
 | `zellij-ps` | Project switcher for Zellij | Rust | `pkgs/zellij-ps/` |
 
+### Overlay Modifications
+
+These entries override upstream nixpkgs packages via `overlays.modifications`. They are also included in `overlays.default`.
+
+| Package | Source | Modification | Location |
+|---------|--------|--------------|----------|
+| `n8n` | `nixpkgs#n8n` | Pins a newer release and fetch hashes | `overlays/mods/default.nix` |
+
 ### Pass-Through Packages
 
 These packages are imported directly from flake inputs with minor modifications: