Use start-sdk's docker-images/<arch>.tar convention

start-sdk pack discovers per-arch tarballs at docker-images/
x86_64.tar and docker-images/aarch64.tar by filename convention,
not via a manifest assets entry. Dropping the invalid
'docker-images: image.tar' assets key and reworking the Makefile
to build one type=docker tarball per arch with arm/x86 single-
arch convenience targets.

.gitignore

@@ -1,4 +1,5 @@
 *.s9pk
 image.tar
+docker-images/
 scripts/embassy.js
 .DS_Store

Makefile

@@ -3,33 +3,77 @@ PKG_VERSION := $(shell yq -r .version manifest.yaml)
 
 TS_FILES := $(shell find ./scripts -name \*.ts 2>/dev/null)
 
+# Where KamadoPool source lives (buildx passes it as a named context).
+KAMADO_SRC ?= ../KamadoPool
+
 .DELETE_ON_ERROR:
 
+# Default: build both arches and verify a universal package.
 all: verify
 
+# Single-arch convenience targets — much faster if you don't have
+# qemu-user-static registered for cross-arch emulation.
+x86: ARCH = x86_64
+x86:
+	@rm -f docker-images/aarch64.tar
+	$(MAKE) ARCH=x86_64
+
+arm: ARCH = aarch64
+arm:
+	@rm -f docker-images/x86_64.tar
+	$(MAKE) ARCH=aarch64
+
 verify: $(PKG_ID).s9pk
 	start-sdk verify s9pk $(PKG_ID).s9pk
+	@echo "Package: $(PKG_ID).s9pk ($(shell du -h $(PKG_ID).s9pk | cut -f1))"
 
 install: $(PKG_ID).s9pk
 	start-cli package install $(PKG_ID).s9pk
 
-$(PKG_ID).s9pk: manifest.yaml instructions.md icon.png LICENSE scripts/embassy.js image.tar
-	start-sdk pack
-
+# ── TypeScript → JS bundle ───────────────────────────────────────────
 scripts/embassy.js: $(TS_FILES)
 	deno run --allow-read --allow-write --allow-env --allow-net scripts/bundle.ts
 
-KAMADO_SRC ?= ../KamadoPool
-PLATFORMS ?= linux/arm64/v8,linux/amd64
-
-image.tar: Dockerfile docker_entrypoint.sh
-	docker buildx build --tag start9/$(PKG_ID)/main:$(PKG_VERSION) \
-		--platform=$(PLATFORMS) \
-		--build-arg ARCH=$(shell uname -m) \
+# ── Docker images, one tarball per arch ──────────────────────────────
+docker-images/x86_64.tar: Dockerfile docker_entrypoint.sh
+ifneq ($(ARCH),aarch64)
+	mkdir -p docker-images
+	docker buildx build \
+		--tag start9/$(PKG_ID)/main:$(PKG_VERSION) \
+		--platform linux/amd64 \
+		--build-arg ARCH=x86_64 \
 		--build-context kamado=$(KAMADO_SRC) \
-		-o type=oci,dest=image.tar .
+		-o type=docker,dest=docker-images/x86_64.tar \
+		.
+endif
+
+docker-images/aarch64.tar: Dockerfile docker_entrypoint.sh
+ifneq ($(ARCH),x86_64)
+	mkdir -p docker-images
+	docker buildx build \
+		--tag start9/$(PKG_ID)/main:$(PKG_VERSION) \
+		--platform linux/arm64 \
+		--build-arg ARCH=aarch64 \
+		--build-context kamado=$(KAMADO_SRC) \
+		-o type=docker,dest=docker-images/aarch64.tar \
+		.
+endif
+
+# ── Pack ─────────────────────────────────────────────────────────────
+$(PKG_ID).s9pk: manifest.yaml instructions.md icon.png LICENSE \
+                scripts/embassy.js \
+                docker-images/x86_64.tar docker-images/aarch64.tar
+ifeq ($(ARCH),x86_64)
+	@echo "start-sdk: packing x86_64 only"
+else ifeq ($(ARCH),aarch64)
+	@echo "start-sdk: packing aarch64 only"
+else
+	@echo "start-sdk: packing universal (x86_64 + aarch64)"
+endif
+	start-sdk pack
 
 clean:
+	rm -rf docker-images
 	rm -f $(PKG_ID).s9pk image.tar scripts/embassy.js
 
-.PHONY: all verify install clean
+.PHONY: all x86 arm verify install clean

manifest.yaml

@@ -31,7 +31,6 @@ assets:
   license: LICENSE
   icon: icon.png
   instructions: instructions.md
-  docker-images: image.tar
 
 main:
   type: docker