fix(ci): harden docker builds and unblock config docs

.github/workflows/docker-release.yml

@@ -36,7 +36,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Set up Docker Builder
-        uses: useblacksmith/setup-docker-builder@v1
+        uses: docker/setup-buildx-action@v3
 
       - name: Login to GitHub Container Registry
         uses: docker/login-action@v3
@@ -137,7 +137,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Set up Docker Builder
-        uses: useblacksmith/setup-docker-builder@v1
+        uses: docker/setup-buildx-action@v3
 
       - name: Login to GitHub Container Registry
         uses: docker/login-action@v3

.github/workflows/install-smoke.yml

@@ -41,7 +41,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Set up Docker Builder
-        uses: useblacksmith/setup-docker-builder@v1
+        uses: docker/setup-buildx-action@v3
 
       # Blacksmith can fall back to the local docker driver, which rejects gha
       # cache export/import. Keep smoke builds driver-agnostic.

.github/workflows/sandbox-common-smoke.yml

@@ -27,7 +27,7 @@ jobs:
           submodules: false
 
       - name: Set up Docker Builder
-        uses: useblacksmith/setup-docker-builder@v1
+        uses: docker/setup-buildx-action@v3
 
       - name: Build minimal sandbox base (USER sandbox)
         shell: bash