test: add resumable isolated test harness

test/harness/main.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+func main() {
+	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer cancel()
+	if err := runCLI(ctx, os.Args[1:]); err != nil {
+		fmt.Fprintln(os.Stderr, "test harness:", err)
+		os.Exit(1)
+	}
+}