CI: Add checks for blueprint compiler / Nix refactors (#6801)

1. Refactored Nix devshell/package to make it easier to keep
LD_LIBRARY_PATH & buildInputs in sync (plus make it easier to re-use in
other Nix environment).
2. Added a CI job to ensure that Blueprints are formatted correctly and
that they will compile using `blueprint-compiler` 0.16.0.
3. Reformatted all Blueprints with `blueprint-compiler format`.

.github/workflows/test.yml

@@ -29,6 +29,7 @@ jobs:
       - alejandra
       - typos
       - translations
+      - blueprint-compiler
       - test-pkg-linux
       - test-debian-12
     steps:
@@ -732,6 +733,35 @@ jobs:
             msgcmp --use-untranslated "$f" po/com.mitchellh.ghostty.pot;
           done
 
+  blueprint-compiler:
+    if: github.repository == 'ghostty-org/ghostty'
+    runs-on: namespace-profile-ghostty-sm
+    timeout-minutes: 60
+    env:
+      ZIG_LOCAL_CACHE_DIR: /zig/local-cache
+      ZIG_GLOBAL_CACHE_DIR: /zig/global-cache
+    steps:
+      - uses: actions/checkout@v4 # Check out repo so we can lint it
+      - 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
+      - uses: cachix/cachix-action@v15
+        with:
+          name: ghostty
+          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
+          skipPush: true
+          useDaemon: false # sometimes fails on short jobs
+      - name: check blueprints
+        run: nix develop -c ./nix/build-support/check-blueprints.sh
+      - name: check unchanged
+        run: git diff --exit-code
+
   test-pkg-linux:
     strategy:
       fail-fast: false