refactor(dotfiles): order default let bindings

docs/TODO.md

@@ -107,7 +107,7 @@
 Review Nix files in entrypoint order:
 
 - [x] `flake.nix`
-- [ ] `src/dotfiles/default.nix`
+- [x] `src/dotfiles/default.nix`
 - [ ] `src/dotfiles/util.nix`
 - [ ] `src/dotfiles/formatter.nix`
 - [ ] `src/dotfiles/apps.nix`

src/dotfiles/default.nix

@@ -19,6 +19,15 @@ let
     root = root + "/modules";
   };
 
+  specialArgs = {
+    inherit
+      inputs
+      self
+      util
+      ;
+    registry = registry.collected;
+  };
+
   guestModules = import ./guests.nix {
     inherit
       inputs
@@ -30,16 +39,6 @@ let
     repositoryModules = modules;
     root = root + "/guests";
   };
-
-  specialArgs = {
-    inherit
-      inputs
-      self
-      util
-      ;
-    registry = registry.collected;
-  };
-
 in
 {
   formatter.${system} =

src/skills/nix-style/rules/let.md

@@ -14,3 +14,15 @@ Do not make an output attrset recursive only to reference sibling outputs.
 Shared convenience bindings hide dependency direction.
 Explicit references show which value owns a concept and which value consumes it.
 
+## Order `let` bindings by dependency
+
+### Rule
+
+Define a `let` binding before other bindings that reference it.
+Use forward references only for intentional recursion or fixed-point wiring.
+
+### Rationale
+
+Nix permits recursive `let` bindings.
+Top-down dependency order makes ordinary wiring easier to read.
+