fix(natu): track application dependencies

AGENTS.md

@@ -122,5 +122,3 @@
   Gitea rebases the synthetic upstream root commit without the `third_party/pi` prefix.
   Preserve `git-subtree-dir` and `git-subtree-split` trailers on Pi vendor commits.
 - The default Pi model for NixOS user configuration is set in `configs/nixos/modules/shell/pi/default.nix`, not in vendored Pi source.
-- Adding `Expr::Apply` traversal to Natu's scope graph changes `let_order` findings.
-  Keep application nodes out of scope traversal until a separate migration addresses the added findings.

configs/nixos/modules/desktop/session/waybar.nix

@@ -7,11 +7,11 @@
 # Waybar: a top status bar reading system state at a glance.
 let
   cfg = config.modules.desktop.session.waybar; # NOLINT(let_order)
-  vpnClient = config.modules.network.vpn-client;
 
   # A Nerd Font Private-Use-Area codepoint as a literal character, decoded
   # through JSON so the glyph survives as bytes rather than an editor paste.
   g = code: builtins.fromJSON ''"\u${code}"'';
+  vpnClient = config.modules.network.vpn-client;
   user = config.user.name;
 
   sleepOffIcon = builtins.fromJSON ''"\udb81\udcb3"'';

src/dotfiles/default.nix

@@ -16,12 +16,6 @@ let
 
   util = import ./util.nix { inherit lib; };
 
-  registry = import ./registry.nix {
-    inherit lib util;
-    hosts = self.nixosConfigurations;
-    root = root + "/registry";
-  };
-
   guestModules = import ./guests.nix {
     inherit
       inputs
@@ -32,6 +26,13 @@ let
     repositoryModules = modules;
     root = root + "/guests";
   };
+
+  registry = import ./registry.nix {
+    inherit lib util;
+    hosts = self.nixosConfigurations;
+    root = root + "/registry";
+  };
+
   modules = import ./modules.nix {
     inherit util;
     root = root + "/modules";

src/natu/scope_graph.rs

@@ -42,7 +42,11 @@ impl ScopeGraph {
                 }
                 self.build_expr(body, scope)
             }
-            ast::Expr::Apply(_) => Vec::new(),
+            ast::Expr::Apply(application) => [
+                self.build_expr(&application.lambda, scope),
+                self.build_expr(&application.argument, scope),
+            ]
+            .concat(),
             ast::Expr::Other(expressions) => expressions
                 .iter()
                 .flat_map(|expression| self.build_expr(expression, scope))