fix(spore): use lib.mkForce to override gc options from base module

The base gc.nix sets nix.gc.options; spore's override conflicted
without mkForce. Also adds a fast eval-only CI job that checks all
NixOS configurations evaluate before the full build runs, catching
option conflicts like this at PR time.

Author: stackptr

.github/workflows/ci.yml

@@ -6,7 +6,23 @@ on:
     branches: main
 
 jobs:
+  eval:
+    name: Evaluate all configurations
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: cachix/install-nix-action@v31
+      with:
+        github_access_token: ${{ secrets.GITHUB_TOKEN }}
+    - name: Check all NixOS configurations evaluate
+      run: |
+        for host in glyph spore zeta; do
+          echo "Evaluating $host..."
+          nix eval .#nixosConfigurations.$host.config.system.build.toplevel.drvPath
+        done
+
   build:
+    needs: eval
     strategy:
       fail-fast: false
       matrix:

hosts/spore/default.nix

@@ -52,8 +52,8 @@
 
   # Stricter GC due to limited disk space (30 GB)
   nix.gc = {
-    dates = "daily";
-    options = "--delete-older-than 7d";
+    dates = lib.mkForce "daily";
+    options = lib.mkForce "--delete-older-than 7d";
   };
 
   nix.settings = {