feat: add nixpkgs-projects pin for CI and local project builds

flake.lock

@@ -33,6 +33,9 @@
         ],
         "nixpkgs-micron": [
           "nixpkgs"
+        ],
+        "nixpkgs-projects": [
+          "nixpkgs"
         ]
       }
     }

flake.nix

@@ -11,7 +11,10 @@
     nixpkgs-howard.follows = "nixpkgs";
     nixpkgs-mermaid.follows = "nixpkgs";
     nixpkgs-micron.follows = "nixpkgs";
+
+    # Project builds (CI + local; follow default unless overridden)
+    nixpkgs-projects.follows = "nixpkgs";
   };
 
-  outputs = { self, nixpkgs, nixpkgs-armer, nixpkgs-bim, nixpkgs-howard, nixpkgs-mermaid, nixpkgs-micron }: { };
+  outputs = { self, nixpkgs, nixpkgs-armer, nixpkgs-bim, nixpkgs-howard, nixpkgs-mermaid, nixpkgs-micron, nixpkgs-projects }: { };
 }