ci: iTerm2 job should run on Namespace and use cache

.github/workflows/update-colorschemes.yml

@@ -7,21 +7,35 @@ on:
 jobs:
   update-iterm2-schemes:
     if: github.repository == 'ghostty-org/ghostty'
-    runs-on: ubuntu-latest
+    runs-on: namespace-profile-ghostty-sm
     permissions:
       # Needed for create-pull-request action
       contents: write
       pull-requests: write
+    env:
+      ZIG_LOCAL_CACHE_DIR: /zig/local-cache
+      ZIG_GLOBAL_CACHE_DIR: /zig/global-cache
     steps:
     - name: Checkout code
       uses: actions/checkout@v4
       with:
         fetch-depth: 0
 
+    - name: Setup Cache
+      uses: namespacelabs/nscloud-cache-action@v1.2.0
+      with:
+        path: |
+          /nix
+          /zig
+
     - name: Setup Nix
       uses: cachix/install-nix-action@v30
       with:
         nix_path: nixpkgs=channel:nixos-unstable
+    - uses: cachix/cachix-action@v15
+      with:
+        name: ghostty
+        authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
 
     - name: Run zig fetch
       id: zig_fetch