Initial benvin-utils monorepo with podgap tool

Add a monorepo for small single-purpose CLI tools that share a common
library, so tools reuse TUI primitives and Kubernetes client bootstrapping
instead of duplicating them.

- common/tui: direction markers, style palette, width-aware padding/layout
- common/kube: in-cluster→kubeconfig client loading + core/metrics clients
- podgap: live TUI comparing pod requests/limits vs actual usage, with
  up/down markers showing per-pod change since the last refresh
- Makefile auto-discovers tool directories: make <tool> | all | install

common/kube/kube.go

@@ -0,0 +1,54 @@
+// Package kube provides shared Kubernetes client bootstrapping for the tools in
+// benvin-utils: a single loader that works both in-cluster and from a local
+// kubeconfig, plus a helper that returns the core and metrics clients together.
+package kube
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
+	"k8s.io/client-go/tools/clientcmd"
+	metricsv "k8s.io/metrics/pkg/client/clientset/versioned"
+)
+
+// LoadConfig resolves a *rest.Config, preferring in-cluster credentials, then
+// the explicit path, then $KUBECONFIG, then ~/.kube/config.
+func LoadConfig(explicit string) (*rest.Config, error) {
+	if cfg, err := rest.InClusterConfig(); err == nil {
+		return cfg, nil
+	}
+	path := explicit
+	if path == "" {
+		path = os.Getenv("KUBECONFIG")
+	}
+	if path == "" {
+		if home, err := os.UserHomeDir(); err == nil {
+			path = filepath.Join(home, ".kube", "config")
+		}
+	}
+	cfg, err := clientcmd.BuildConfigFromFlags("", path)
+	if err != nil {
+		return nil, fmt.Errorf("load kubeconfig %q: %w", path, err)
+	}
+	return cfg, nil
+}
+
+// Clients returns the core and metrics clientsets for the resolved config.
+func Clients(explicit string) (kubernetes.Interface, metricsv.Interface, error) {
+	cfg, err := LoadConfig(explicit)
+	if err != nil {
+		return nil, nil, err
+	}
+	core, err := kubernetes.NewForConfig(cfg)
+	if err != nil {
+		return nil, nil, fmt.Errorf("core client: %w", err)
+	}
+	mc, err := metricsv.NewForConfig(cfg)
+	if err != nil {
+		return nil, nil, fmt.Errorf("metrics client: %w", err)
+	}
+	return core, mc, nil
+}