ci: evaluate the darwin host configuration

The eval loop covered only the NixOS hosts, so the nix-darwin host could
break unnoticed. Add an eval step for darwinConfigurations.lyrathorpe-mac.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -32,9 +32,9 @@ jobs:
         run: nix build --print-build-logs '.#checks.x86_64-linux.formatting'
 
       # Evaluate (not build) each host's toplevel so eval errors fail CI cheaply.
-      # aarch64 hosts evaluate fine on an x86_64 runner; only building would need
-      # emulation, which we deliberately avoid here.
-      - name: Evaluate host configurations
+      # aarch64 / darwin hosts evaluate fine on an x86_64 runner; only building
+      # would need emulation, which we deliberately avoid here.
+      - name: Evaluate NixOS host configurations
         run: |
           set -euo pipefail
           for host in lyrathorpe-mbp lyrathorpe-x1c emmathorpe-edaas; do
@@ -43,3 +43,13 @@ jobs:
             echo
             echo "::endgroup::"
           done
+
+      - name: Evaluate Darwin host configurations
+        run: |
+          set -euo pipefail
+          for host in lyrathorpe-mac; do
+            echo "::group::eval $host"
+            nix eval --raw ".#darwinConfigurations.$host.config.system.build.toplevel.drvPath"
+            echo
+            echo "::endgroup::"
+          done