nextcloud: use a named build stage for docker:cli, not ARG-in-COPY-from

the legacy (non-BuildKit) docker build this host runs doesn't expand ARGs
inside COPY --from — only FROM. Give it its own named stage instead

modules/nextcloud/Dockerfile

@@ -11,6 +11,10 @@ ARG BUILD_BASE
 ARG RUNTIME_BASE
 ARG DOCKER_CLI
 
+# Named so the final stage's COPY --from can reference a stage, not an ARG — the legacy builder
+# this host still runs doesn't expand ARGs inside COPY --from, only inside FROM.
+FROM ${DOCKER_CLI} AS dockercli
+
 FROM ${BUILD_BASE} AS build
 # Compiled under /app/modules so `@novox/mesh-sdk` resolves upward into the base's own
 # node_modules — the module is compiled against exactly the sdk it will run against. The compiler
@@ -22,15 +26,12 @@ RUN node /app/node_modules/typescript/bin/tsc client.ts index.ts tools/index.ts
       --module NodeNext --moduleResolution NodeNext --target ES2022 --outDir dist
 
 FROM ${RUNTIME_BASE}
-# ARGs declared before the first FROM are out of scope past it; redeclared here so COPY --from
-# below can see it.
-ARG DOCKER_CLI
 COPY --from=build /app/modules/nextcloud/dist /app/modules/nextcloud/dist
 # occ runs inside nextcloud's own container, reached over the mounted docker socket — which needs
 # the docker CLI itself present here, not only the socket. Copied from Docker's own official client
 # image rather than apt-installed, so this stays the one binary and nothing else (no daemon, no
 # systemd unit, no package manager tree pulled in for it).
-COPY --from=${DOCKER_CLI} /usr/local/bin/docker /usr/local/bin/docker
+COPY --from=dockercli /usr/local/bin/docker /usr/local/bin/docker
 # Every serve-time entrypoint, loaded by the runtime in serve mode: tools and events serve, and a
 # provider's provisioner runs its reconcile loop in the same process, with the broker connected —
 # the convention novox/hq issues 060/061 settled. A container that instead ran only its