fix(nix): resolve build issues and add CI verification (#668)

* ci: add Nix build verification to pytest workflow

Add a verification step to the CI pipeline that validates the Nix package builds successfully on each run. The step uses 'nix build --no-link' to verify the flake builds without creating artifacts.

This provides early detection of Nix packaging issues with minimal overhead, reusing the existing Nix installation on Linux and macOS runners.

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Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

* fix(nix): add setuptools to ruamel-yaml-clib build dependencies

Add pyproject override to ensure ruamel-yaml-clib has setuptools available during build. This fixes Nix build failures where the package requires setuptools but doesn't declare it as a native build input.

🤖 Generated with [Claude Code](https://claude.com/claude-code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Happy <yesreply@happy.engineering>

.github/workflows/pytest.yml

@@ -256,6 +256,12 @@ jobs:
           fi
           
           echo "$HOME/.nix-profile/bin" >> $GITHUB_PATH
+      - name: Verify Nix package build
+        if: runner.os != 'Windows'  # Nix only supported on Linux/macOS
+        shell: bash
+        run: |
+          # Verify the flake builds successfully
+          nix build --no-link
       - name: Install uv
         shell: bash
         run: curl -LsSf https://astral.sh/uv/install.sh | sh

flake.nix

@@ -50,7 +50,14 @@
         sourcePreference = "wheel"; # or sourcePreference = "sdist";
       };
 
-      pyprojectOverrides = _final: _prev: {};
+      pyprojectOverrides = final: prev: {
+        # Add setuptools for packages that need it during build
+        ruamel-yaml-clib = prev.ruamel-yaml-clib.overrideAttrs (old: {
+          nativeBuildInputs = (old.nativeBuildInputs or []) ++ [
+            final.setuptools
+          ];
+        });
+      };
 
       python = pkgs.python311;