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

Makefile

@@ -0,0 +1,67 @@
+# benvin-utils — a collection of small tools. Each tool is a directory
+# containing a `package main`; the shared library lives under common/.
+#
+# Tools are auto-discovered, so adding a new tool directory needs no Makefile
+# edits: `make all`, `make install`, and `make <tool>` just pick it up.
+
+GO      ?= go
+BINDIR  ?= bin
+# GOBIN, else $(go env GOPATH)/bin — where `make install` puts binaries.
+GOBIN   ?= $(shell $(GO) env GOBIN)
+ifeq ($(GOBIN),)
+GOBIN   := $(shell $(GO) env GOPATH)/bin
+endif
+
+# A directory is a "tool" if it holds at least one *.go file with `package main`
+# and is not the shared library or hidden/dot dir.
+TOOLS := $(sort $(patsubst %/,%,$(dir $(shell grep -rl --include='*.go' '^package main' . 2>/dev/null))))
+TOOLS := $(filter-out ./common%,$(TOOLS))
+TOOLS := $(patsubst ./%,%,$(TOOLS))
+
+.DEFAULT_GOAL := all
+
+.PHONY: all
+all: $(TOOLS) ## Build every tool into ./bin
+
+# Pattern rule: `make <tool>` builds that one tool into ./bin/<tool>.
+.PHONY: $(TOOLS)
+$(TOOLS): %: | $(BINDIR)
+	@echo "  build  $@"
+	@$(GO) build -o $(BINDIR)/$@ ./$@
+
+$(BINDIR):
+	@mkdir -p $(BINDIR)
+
+.PHONY: install
+install: ## Install every tool into $(GOBIN)
+	@echo "  install → $(GOBIN)"
+	@$(GO) install ./...
+
+.PHONY: test
+test: ## Run all tests
+	@$(GO) test ./...
+
+.PHONY: tidy
+tidy: ## go mod tidy
+	@$(GO) mod tidy
+
+.PHONY: fmt vet
+fmt: ; @$(GO) fmt ./...
+vet: ; @$(GO) vet ./...
+
+.PHONY: clean
+clean: ## Remove built binaries
+	@rm -rf $(BINDIR)
+
+.PHONY: list
+list: ## List discovered tools
+	@echo $(TOOLS)
+
+.PHONY: help
+help: ## Show this help
+	@echo "benvin-utils — tools: $(TOOLS)"
+	@echo
+	@grep -hE '^[a-zA-Z_$$()%-]+:.*?## ' $(MAKEFILE_LIST) | \
+		sort | awk 'BEGIN{FS=":.*?## "}{printf "  \033[36m%-12s\033[0m %s\n", $$1, $$2}'
+	@echo
+	@echo "  make <tool>   Build one tool (e.g. make podgap)"