fix: apply claude-code overlay to NixOS modules

The custom claude-code package (from GCS) was only being applied to
darwinModules, causing NixOS systems to use the older version from
nixpkgs-unstable instead of the updated version from packages/claude-code.

Extract claudeCodeOverlay as a shared definition and apply it to all
module sets: nixosModules, nixosModulesUnstable, and darwinModules.

Executed-By: mayor
Role: mayor

flake.nix

@@ -60,6 +60,12 @@
   };
 
   outputs = { self, nixpkgs, nixpkgs-unstable, ... } @ inputs: let
+    # Overlay to use our custom claude-code package from GCS
+    # (needed for corporate networks that block npm registry)
+    claudeCodeOverlay = ufinal: uprev: {
+      claude-code = uprev.callPackage ./packages/claude-code {};
+    };
+
     # Shared overlay function to reduce duplication across module sets
     # Parameters:
     #   unstableOverlays: Additional overlays to apply when importing nixpkgs-unstable
@@ -93,7 +99,9 @@
       ./roles
       inputs.home-manager.nixosModules.home-manager
       {
-        nixpkgs.overlays = [ (mkBaseOverlay {}) ];
+        nixpkgs.overlays = [
+          (mkBaseOverlay { unstableOverlays = [ claudeCodeOverlay ]; })
+        ];
       }
       (mkHomeManagerConfig {
         sharedModules = [ inputs.plasma-manager.homeModules.plasma-manager ];
@@ -106,7 +114,9 @@
       inputs.home-manager-unstable.nixosModules.home-manager
       inputs.jovian.nixosModules.jovian
       {
-        nixpkgs.overlays = [ (mkBaseOverlay {}) ];
+        nixpkgs.overlays = [
+          (mkBaseOverlay { unstableOverlays = [ claudeCodeOverlay ]; })
+        ];
       }
       (mkHomeManagerConfig {
         sharedModules = [ inputs.plasma-manager-unstable.homeModules.plasma-manager ];
@@ -118,15 +128,7 @@
       inputs.home-manager.darwinModules.home-manager
       {
         nixpkgs.overlays = [
-          (mkBaseOverlay {
-            # Override claude-code in unstable to use our custom GCS-based build
-            # (needed for corporate networks that block npm registry)
-            unstableOverlays = [
-              (ufinal: uprev: {
-                claude-code = uprev.callPackage ./packages/claude-code {};
-              })
-            ];
-          })
+          (mkBaseOverlay { unstableOverlays = [ claudeCodeOverlay ]; })
         ];
       }
       (mkHomeManagerConfig { sharedModules = []; })