feat(shells): add opencode dev shell with mkOpencodeRules demo

flake.nix

@@ -78,11 +78,11 @@
 
     # Development shells for various programming environments
     # Usage: nix develop .#<shell-name>
-    # Available shells: default, python, devops
+    # Available shells: default, python, devops, opencode
     devShells = forAllSystems (system: let
       pkgs = pkgsFor system;
     in
-      import ./shells {inherit pkgs;});
+      import ./shells {inherit pkgs inputs;});
 
     # Formatter for 'nix fmt'
     formatter = forAllSystems (system: (pkgsFor system).alejandra);