build: add dynamic version injection via ldflags and Makefile

- Add cmd.Version variable set at build time via -ldflags
- Fix Dockerfile ldflags path to use cmd.Version instead of main.version
- Add Makefile with auto-detection from git tags (git describe)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile

@@ -26,7 +26,7 @@ RUN set -eux; \
     fi; \
     if [ -n "$TAGS" ]; then TAGS="-tags $TAGS"; fi; \
     CGO_ENABLED=0 GOOS=linux \
-    go build -ldflags="-s -w -X main.version=${VERSION}" \
+    go build -ldflags="-s -w -X github.com/nextlevelbuilder/goclaw/cmd.Version=${VERSION}" \
     ${TAGS} -o /out/goclaw .
 
 # ── Stage 2: Runtime ──

Makefile

@@ -0,0 +1,17 @@
+VERSION ?= $(shell git describe --tags --always --dirty 2>/dev/null || echo dev)
+LDFLAGS  = -s -w -X github.com/nextlevelbuilder/goclaw/cmd.Version=$(VERSION)
+BINARY   = goclaw
+
+.PHONY: build run clean version
+
+build:
+	CGO_ENABLED=0 go build -ldflags="$(LDFLAGS)" -o $(BINARY) .
+
+run: build
+	./$(BINARY)
+
+clean:
+	rm -f $(BINARY)
+
+version:
+	@echo $(VERSION)

cmd/root.go

@@ -9,6 +9,9 @@ import (
 	"github.com/nextlevelbuilder/goclaw/pkg/protocol"
 )
 
+// Version is set at build time via -ldflags "-X github.com/nextlevelbuilder/goclaw/cmd.Version=v1.0.0"
+var Version = "dev"
+
 var (
 	cfgFile string
 	verbose bool
@@ -46,7 +49,7 @@ func versionCmd() *cobra.Command {
 		Use:   "version",
 		Short: "Print version information",
 		Run: func(cmd *cobra.Command, args []string) {
-			fmt.Printf("goclaw v0.2.0 (protocol %d)\n", protocol.ProtocolVersion)
+			fmt.Printf("goclaw %s (protocol %d)\n", Version, protocol.ProtocolVersion)
 		},
 	}
 }