fix: correct devenv.yaml git-hooks input syntax

Use 'follows: nixpkgs' struct syntax instead of bare string 'nixpkgs'
for the input reference, as required by devenv's YAML parser.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: teaguesterling

devenv.yaml

@@ -5,7 +5,8 @@ inputs:
   git-hooks:
     url: github:cachix/git-hooks.nix
     inputs:
-      nixpkgs: nixpkgs
+      nixpkgs:
+        follows: nixpkgs
 
 # If you're using non-OSS software, you can set allowUnfree to true.
 # allowUnfree: true