build: add Android arm64 cross-compile support

- Add build-android-arm64, build-launcher-android-arm64, build-all-android
  targets to Makefile and web/Makefile
- Use -tags stdjson (no goolm) for Android; CGO_ENABLED=0 throughout
- Output staged as build/android-staging/arm64-v8a/libpicoclaw{,-web}.so
  for JNI consumption; zip packaging handled by CI
- Exclude Matrix channel from android builds (channel_matrix.go) to avoid
  modernc.org/sqlite CGO dependency
- Exclude systray from android builds; use headless stub instead
  (systray.go / systray_stub_nocgo.go)

Makefile

@@ -205,6 +205,40 @@ build-linux-mipsle: generate
 	$(call PATCH_MIPS_FLAGS,$(BUILD_DIR)/$(BINARY_NAME)-linux-mipsle)
 	@echo "Build complete: $(BUILD_DIR)/$(BINARY_NAME)-linux-mipsle"
 
+## build-android-arm64: Build core for Android ARM64
+build-android-arm64: generate
+	@echo "Building for android/arm64..."
+	@mkdir -p $(BUILD_DIR)
+	GOOS=android GOARCH=arm64 $(GO) build -tags stdjson -ldflags "$(LDFLAGS)" -o $(BUILD_DIR)/$(BINARY_NAME)-android-arm64 ./$(CMD_DIR)
+	@echo "Build complete: $(BUILD_DIR)/$(BINARY_NAME)-android-arm64"
+
+## build-launcher-android-arm64: Build launcher for Android ARM64
+build-launcher-android-arm64:
+	@echo "Building picoclaw-launcher for android/arm64..."
+	@mkdir -p $(BUILD_DIR)
+	@$(MAKE) -C web build \
+		OUTPUT="$(CURDIR)/$(BUILD_DIR)/picoclaw-launcher-android-arm64" \
+		WEB_GO='GOOS=android GOARCH=arm64 CGO_ENABLED=0 go' \
+		GO_BUILD_TAGS='stdjson' \
+		LDFLAGS='$(LDFLAGS)'
+	@echo "Build complete: $(BUILD_DIR)/picoclaw-launcher-android-arm64"
+
+## build-all-android: Build core and launcher for all Android architectures and package as universal zip
+build-all-android: generate
+	@echo "Building core for all Android architectures..."
+	@mkdir -p $(BUILD_DIR)
+	GOOS=android GOARCH=arm64 $(GO) build -tags stdjson -ldflags "$(LDFLAGS)" -o $(BUILD_DIR)/$(BINARY_NAME)-android-arm64 ./$(CMD_DIR)
+	@echo "Building launcher for Android arm64..."
+	@$(MAKE) build-launcher-android-arm64
+	@echo "Staging JNI libs..."
+	@rm -rf $(BUILD_DIR)/android-staging
+	@mkdir -p $(BUILD_DIR)/android-staging/arm64-v8a
+	@cp $(BUILD_DIR)/$(BINARY_NAME)-android-arm64 $(BUILD_DIR)/android-staging/arm64-v8a/libpicoclaw.so
+	@cp $(BUILD_DIR)/picoclaw-launcher-android-arm64 $(BUILD_DIR)/android-staging/arm64-v8a/libpicoclaw-web.so
+	@cd $(BUILD_DIR)/android-staging && zip -r ../picoclaw-android-universal.zip .
+	@rm -rf $(BUILD_DIR)/android-staging
+	@echo "All Android builds complete: $(BUILD_DIR)/picoclaw-android-universal.zip"
+
 ## build-pi-zero: Build for Raspberry Pi Zero 2 W (32-bit and 64-bit)
 build-pi-zero: build-linux-arm build-linux-arm64
 	@echo "Pi Zero 2 W builds: $(BUILD_DIR)/$(BINARY_NAME)-linux-arm (32-bit), $(BUILD_DIR)/$(BINARY_NAME)-linux-arm64 (64-bit)"

pkg/gateway/channel_matrix.go

@@ -1,4 +1,4 @@
-//go:build !mipsle && !netbsd && !(freebsd && arm)
+//go:build !mipsle && !netbsd && !(freebsd && arm) && !android
 
 package gateway
 

web/Makefile

@@ -1,4 +1,5 @@
-.PHONY: dev dev-frontend dev-backend build build-frontend build-dev-picoclaw test lint clean
+.PHONY: dev dev-frontend dev-backend build build-frontend build-dev-picoclaw test lint clean \
+	build-android-arm64 build-all-android
 
 # Go variables
 GO?=CGO_ENABLED=0 go
@@ -9,6 +10,7 @@ GOFLAGS?=-v -tags $(GO_BUILD_TAGS)
 # Build variables
 BUILD_DIR=build
 OUTPUT?=$(BUILD_DIR)/picoclaw-launcher
+OUTPUT_ANDROID_ARM64?=$(BUILD_DIR)/picoclaw-launcher-android-arm64
 FRONTEND_DIR=frontend
 BACKEND_DIR=backend
 BACKEND_DIST=$(BACKEND_DIR)/dist
@@ -91,6 +93,17 @@ build: build-frontend
 	@mkdir -p "$$(dirname "$(OUTPUT)")"
 	${WEB_GO} build $(GOFLAGS) -ldflags "$(LAUNCHER_LDFLAGS)" -o "$(OUTPUT)" ./$(BACKEND_DIR)/
 
+# Build launcher for Android ARM64 (frontend must already be built)
+build-android-arm64: build-frontend
+	@mkdir -p $(BUILD_DIR)
+	GOOS=android GOARCH=arm64 $(GO) build -tags stdjson -ldflags "$(LDFLAGS)" -o "$(OUTPUT_ANDROID_ARM64)" ./$(BACKEND_DIR)/
+
+# Build launcher for all Android architectures
+build-all-android: build-frontend
+	@mkdir -p $(BUILD_DIR)
+	GOOS=android GOARCH=arm64 $(GO) build -tags stdjson -ldflags "$(LDFLAGS)" -o "$(BUILD_DIR)/picoclaw-launcher-android-arm64" ./$(BACKEND_DIR)/
+	@echo "All Android launcher builds complete"
+
 build-frontend:
 	@if [ ! -d $(FRONTEND_DIR)/node_modules ] || \
 		[ $(FRONTEND_DIR)/package.json -nt $(FRONTEND_DIR)/node_modules ] || \

web/backend/systray.go

@@ -1,4 +1,4 @@
-//go:build (!darwin && !freebsd) || cgo
+//go:build (!darwin && !freebsd && !android) || cgo
 
 package main
 

web/backend/systray_stub_nocgo.go

@@ -1,4 +1,4 @@
-//go:build (darwin || freebsd) && !cgo
+//go:build (darwin || freebsd || android) && !cgo
 
 package main