add Makefile with auto-signing for macOS

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Makefile

@@ -0,0 +1,29 @@
+.PHONY: build install clean test
+
+BINARY := gt
+BUILD_DIR := .
+
+# Get version info for ldflags
+VERSION := $(shell git describe --tags --always --dirty 2>/dev/null || echo "dev")
+COMMIT := $(shell git rev-parse --short HEAD 2>/dev/null || echo "unknown")
+BUILD_TIME := $(shell date -u +"%Y-%m-%dT%H:%M:%SZ")
+
+LDFLAGS := -X github.com/steveyegge/gastown/internal/cmd.Version=$(VERSION) \
+           -X github.com/steveyegge/gastown/internal/cmd.Commit=$(COMMIT) \
+           -X github.com/steveyegge/gastown/internal/cmd.BuildTime=$(BUILD_TIME)
+
+build:
+	go build -ldflags "$(LDFLAGS)" -o $(BUILD_DIR)/$(BINARY) ./cmd/gt
+ifeq ($(shell uname),Darwin)
+	@codesign -s - -f $(BUILD_DIR)/$(BINARY) 2>/dev/null || true
+	@echo "Signed $(BINARY) for macOS"
+endif
+
+install: build
+	cp $(BUILD_DIR)/$(BINARY) ~/bin/$(BINARY)
+
+clean:
+	rm -f $(BUILD_DIR)/$(BINARY)
+
+test:
+	go test ./...