Makefile: build with CGO_ENABLED=0

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Makefile

@@ -3,6 +3,7 @@
 MCR     := mcr.svc.mcp.metacircular.net:8443
 VERSION := $(shell git describe --tags --always --dirty 2>/dev/null || echo dev)
 LDFLAGS := -trimpath -ldflags="-s -w -X main.version=$(VERSION)"
+CGO     := CGO_ENABLED=0
 
 binaries: metacrypt metacrypt-web
 
@@ -15,10 +16,10 @@ proto:
 		proto/metacrypt/v2/*.proto
 
 metacrypt:
-	go build $(LDFLAGS) -o metacrypt ./cmd/metacrypt
+	$(CGO) go build $(LDFLAGS) -o metacrypt ./cmd/metacrypt
 
 metacrypt-web:
-	go build $(LDFLAGS) -o metacrypt-web ./cmd/metacrypt-web
+	$(CGO) go build $(LDFLAGS) -o metacrypt-web ./cmd/metacrypt-web
 
 build:
 	go build ./...