feat: Build and publish vantagectl

The scratch runtime stage copies an explicit /tmp: restore extracts an
archive there before verifying it, and a scratch image has none.

shared/ now fans out to four Go images rather than three.

.gitea/workflows/server-deploy.yml

@@ -71,15 +71,16 @@ jobs:
                       fi
                   }
 
-                  # The three Go images build from the repo root and COPY
+                  # The four Go images build from the repo root and COPY
                   # shared/ plus their own directory, so shared/ rebuilds all
-                  # three. proto/ is in server's list as insurance: the
+                  # four. proto/ is in server's list as insurance: the
                   # generated pb is committed under server/, but a proto change
                   # that someone regenerates in the same push should not depend
                   # on that ordering.
                   flag server    '^(server/|shared/|proto/|default_steps/|go\.work)'
                   flag sitesvc   '^(sitesvc/|shared/|go\.work)'
                   flag admin     '^(admin/|shared/|go\.work)'
+                  flag vantagectl '^(vantagectl/|shared/|go\.work)'
 
                   # The three Next images and the docs site use their own
                   # directory as the build context, so nothing outside it can
@@ -159,6 +160,14 @@ jobs:
                   docker build -t "$IMAGE" -f admin/Dockerfile .
                   docker push "$IMAGE"
 
+            - name: Build and push vantagectl image
+              if: steps.changed.outputs.vantagectl == 'true'
+              run: |
+                  IMAGE="${{ vars.DOCKER_HOST }}/${{ github.repository_owner }}/vantage/vantagectl:latest"
+                  # Root context: vantagectl depends on the shared module.
+                  docker build -t "$IMAGE" -f vantagectl/Dockerfile .
+                  docker push "$IMAGE"
+
             - name: Build and push adminsite image
               if: steps.changed.outputs.adminsite == 'true'
               run: |

.gitea/workflows/vantagectl-release.yml

@@ -0,0 +1,60 @@
+name: vantagectl Release
+
+on:
+    push:
+        tags:
+            - "vantagectl/v*"
+
+jobs:
+    build:
+        runs-on: ubuntu-docker
+        container: node:26
+        steps:
+            - name: Checkout
+              uses: actions/checkout@v4
+
+            - name: Set up Go
+              uses: actions/setup-go@v5
+              with:
+                  go-version: "1.26"
+                  cache: true
+                  cache-dependency-path: vantagectl/go.sum
+
+            - name: Extract version
+              id: version
+              run: echo "VERSION=${GITHUB_REF_NAME#vantagectl/}" >> $GITHUB_OUTPUT
+
+            - name: Test
+              working-directory: vantagectl
+              run: go test ./...
+
+            - name: Build
+              working-directory: vantagectl
+              env:
+                  VERSION: ${{ steps.version.outputs.VERSION }}
+              run: |
+                  mkdir -p dist
+                  for target in linux/amd64 linux/arm64 darwin/arm64 windows/amd64; do
+                      goos="${target%/*}"
+                      goarch="${target#*/}"
+                      out="dist/vantagectl-${goos}-${goarch}"
+                      if [ "$goos" = "windows" ]; then out="${out}.exe"; fi
+                      CGO_ENABLED=0 GOOS="$goos" GOARCH="$goarch" go build \
+                        -ldflags="-s -w -X main.Version=${VERSION}" \
+                        -o "$out" .
+                  done
+
+            - name: Checksums
+              working-directory: vantagectl/dist
+              run: sha256sum vantagectl-* > checksums.txt
+
+            - name: Create release
+              uses: https://gitea.com/actions/gitea-release-action@v1
+              with:
+                  token: ${{ secrets.RELEASE_TOKEN }}
+                  files: |
+                      vantagectl/dist/vantagectl-linux-amd64
+                      vantagectl/dist/vantagectl-linux-arm64
+                      vantagectl/dist/vantagectl-darwin-arm64
+                      vantagectl/dist/vantagectl-windows-amd64.exe
+                      vantagectl/dist/checksums.txt

vantagectl/Dockerfile

@@ -0,0 +1,36 @@
+# Build stage
+#
+# Context is the repository root, not vantagectl/, because vantagectl depends on
+# the shared module through a replace directive.
+FROM golang:1.26 AS builder
+
+WORKDIR /src
+
+# Manifests first so the dependency layer caches independently of source edits.
+COPY shared/go.mod shared/go.sum ./shared/
+COPY vantagectl/go.mod vantagectl/go.sum ./vantagectl/
+RUN cd vantagectl && go mod download
+
+COPY shared/ ./shared/
+COPY vantagectl/ ./vantagectl/
+
+ARG VERSION=dev
+RUN cd vantagectl && CGO_ENABLED=0 GOOS=linux go build \
+      -ldflags="-s -w -X main.Version=${VERSION}" -o /vantagectl .
+
+# Staged so the scratch image below can have a /tmp. It cannot mkdir one
+# itself — scratch has no shell.
+RUN mkdir -p /staging/tmp && chmod 1777 /staging/tmp
+
+# Runtime stage
+FROM scratch
+
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+
+# restore extracts an archive here before verifying its checksums, and backup
+# stages nothing but still inherits os.MkdirTemp's requirements. Without this
+# every restore stops at "temp dir: stat /tmp: no such file or directory".
+COPY --from=builder /staging/tmp /tmp
+COPY --from=builder /vantagectl /vantagectl
+
+ENTRYPOINT ["/vantagectl"]