fix(channels): reply via reply_target and improve local Docker cache reuse

dev/README.md

@@ -163,5 +163,7 @@ Note: local `deny` focuses on license/source policy; advisory scanning is handle
 ### Build cache notes
 
 - Both `Dockerfile` and `dev/ci/Dockerfile` use BuildKit cache mounts for Cargo registry/git data.
+- The root `Dockerfile` also caches Rust `target/` (`id=zeroclaw-target`) to speed repeat local image builds.
 - Local CI reuses named Docker volumes for Cargo registry/git and target outputs.
+- `./dev/ci.sh docker-smoke` and `./dev/ci.sh all` now use `docker buildx` local cache at `.cache/buildx-smoke` when available.
 - The CI image keeps Rust toolchain defaults from `rust:1.92-slim` and installs pinned toolchain `1.92.0` (no custom `CARGO_HOME`/`RUSTUP_HOME` overrides), preventing repeated toolchain bootstrapping on each run.

dev/ci.sh

@@ -11,12 +11,32 @@ else
 fi
 
 compose_cmd=(docker compose -f "$COMPOSE_FILE")
+SMOKE_CACHE_DIR="${SMOKE_CACHE_DIR:-.cache/buildx-smoke}"
 
 run_in_ci() {
   local cmd="$1"
   "${compose_cmd[@]}" run --rm local-ci bash -c "$cmd"
 }
 
+build_smoke_image() {
+  if docker buildx version >/dev/null 2>&1; then
+    mkdir -p "$SMOKE_CACHE_DIR"
+    local build_args=(
+      --load
+      --target dev
+      --cache-to "type=local,dest=$SMOKE_CACHE_DIR,mode=max"
+      -t zeroclaw-local-smoke:latest
+      .
+    )
+    if [ -f "$SMOKE_CACHE_DIR/index.json" ]; then
+      build_args=(--cache-from "type=local,src=$SMOKE_CACHE_DIR" "${build_args[@]}")
+    fi
+    docker buildx build "${build_args[@]}"
+  else
+    DOCKER_BUILDKIT=1 docker build --target dev -t zeroclaw-local-smoke:latest .
+  fi
+}
+
 print_help() {
   cat <<'EOF'
 ZeroClaw Local CI in Docker
@@ -88,7 +108,7 @@ case "$1" in
     ;;
 
   docker-smoke)
-    docker build --target dev -t zeroclaw-local-smoke:latest .
+    build_smoke_image
     docker run --rm zeroclaw-local-smoke:latest --version
     ;;
 
@@ -98,7 +118,7 @@ case "$1" in
     run_in_ci "cargo build --release --locked --verbose"
     run_in_ci "cargo deny check licenses sources"
     run_in_ci "cargo audit"
-    docker build --target dev -t zeroclaw-local-smoke:latest .
+    build_smoke_image
     docker run --rm zeroclaw-local-smoke:latest --version
     ;;