fix CI: use runs-on host, remove install-nix-action

Runner has label 'host' not 'docker'. Jobs were stuck in 'waiting to
run' because no runner matched the docker label. Also removed the
cachix/install-nix-action steps since Nix is already available on the
host runner.

.forgejo/workflows/ci.yml

@@ -4,31 +4,21 @@ on: [pull_request]
 
 jobs:
   flake-check:
-    runs-on: docker
+    runs-on: host
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Install Nix
-        uses: cachix/install-nix-action@v27
-        with:
-          nix_path: nixpkgs=channel:nixos-unstable
-
       - name: Run flake check
         run: nix flake check --impure
 
   build-hosts:
     needs: flake-check
-    runs-on: docker
+    runs-on: host
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Install Nix
-        uses: cachix/install-nix-action@v27
-        with:
-          nix_path: nixpkgs=channel:nixos-unstable
-
       - name: Build cryodev-main
         run: nix build .#nixosConfigurations.cryodev-main.config.system.build.toplevel --impure
 

.forgejo/workflows/deploy.yml

@@ -7,31 +7,21 @@ on:
 
 jobs:
   flake-check:
-    runs-on: docker
+    runs-on: host
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Install Nix
-        uses: cachix/install-nix-action@v27
-        with:
-          nix_path: nixpkgs=channel:nixos-unstable
-
       - name: Run flake check
         run: nix flake check --impure
 
   deploy-cryodev-main:
     needs: flake-check
-    runs-on: docker
+    runs-on: host
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Install Nix
-        uses: cachix/install-nix-action@v27
-        with:
-          nix_path: nixpkgs=channel:nixos-unstable
-
       - name: Set up SSH
         env:
           DEPLOY_KEY: ${{ secrets.DEPLOY_SSH_KEY }}