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

podgap/main.go

@@ -0,0 +1,73 @@
+// Command podgap shows the gap between what Kubernetes pods reserve
+// (requests/limits) and what they actually use, live in a terminal UI.
+//
+// The default mode opens an interactive TUI that refreshes in place and marks
+// whether each pod's usage rose or fell since the last refresh. The json/csv
+// output modes are one-shot dumps for scripting.
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"time"
+
+	"git.unkin.net/unkin/benvin-utils/common/kube"
+
+	"github.com/spf13/pflag"
+)
+
+type options struct {
+	namespace  string
+	sortKey    string
+	top        int
+	interval   time.Duration
+	output     string
+	kubeconfig string
+	overOnly   bool
+	underOnly  bool
+	threshold  float64
+}
+
+func main() {
+	opts := options{}
+	pflag.StringVarP(&opts.namespace, "namespace", "n", "", "namespace to inspect (default: all namespaces)")
+	pflag.StringVarP(&opts.sortKey, "sort", "s", "cpu-waste", "sort by: cpu-waste, mem-waste, cpu-util, mem-util, cpu-use, mem-use, name")
+	pflag.IntVar(&opts.top, "top", 0, "show only the top N rows after sorting (0 = all)")
+	pflag.DurationVarP(&opts.interval, "interval", "i", 0, "TUI refresh interval (e.g. 5s); 0 = default 3s")
+	pflag.StringVarP(&opts.output, "output", "o", "tui", "output: tui (interactive), json, csv")
+	pflag.StringVar(&opts.kubeconfig, "kubeconfig", "", "path to kubeconfig (default: $KUBECONFIG or ~/.kube/config)")
+	pflag.BoolVar(&opts.overOnly, "over", false, "show only over-provisioned pods (util below --threshold)")
+	pflag.BoolVar(&opts.underOnly, "under", false, "show only under-provisioned pods (usage above request or limit)")
+	pflag.Float64Var(&opts.threshold, "threshold", 0.5, "utilization fraction below which a pod is 'over-provisioned' (with --over)")
+	pflag.Parse()
+
+	if err := run(opts); err != nil {
+		fmt.Fprintln(os.Stderr, "error:", err)
+		os.Exit(1)
+	}
+}
+
+func run(opts options) error {
+	core, mc, err := kube.Clients(opts.kubeconfig)
+	if err != nil {
+		return err
+	}
+
+	// json/csv are one-shot, script-friendly dumps; anything else opens the TUI.
+	switch opts.output {
+	case "json", "csv":
+		rows, err := collect(context.Background(), core, mc, opts.namespace)
+		if err != nil {
+			return err
+		}
+		rows = filterRows(rows, opts)
+		sortRows(rows, opts.sortKey)
+		if opts.top > 0 && len(rows) > opts.top {
+			rows = rows[:opts.top]
+		}
+		return render(os.Stdout, rows, opts.output)
+	default:
+		return runTUI(core, mc, opts)
+	}
+}