ci: use a namespace cache

.github/workflows/test.yml

@@ -3,12 +3,21 @@ name: Test
 jobs:
   build:
     runs-on: namespace-profile-ghostty-macos
+    env:
+      ZIG_LOCAL_CACHE_DIR: /zig/local-cache
+      ZIG_GLOBAL_CACHE_DIR: /zig/global-cache
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
 
-      # Install Nix and use that to run our tests so our environment matches exactly.
-      - uses: cachix/install-nix-action@v23
+      - name: Setup Cache
+        uses: namespacelabs/nscloud-cache-action@v1.2.0
+        with:
+          path: |
+            /nix
+            /zig
+
+      - uses: cachix/install-nix-action@v30
         with:
           nix_path: nixpkgs=channel:nixos-unstable