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/README.md

@@ -0,0 +1,74 @@
+# podgap
+
+Shows the **gap** between what Kubernetes pods reserve (requests/limits) and what
+they actually use — live, in a terminal UI that refreshes in place and marks
+whether each pod's usage rose (▲) or fell (▼) since the last refresh. Use it to
+find over-provisioned pods (reserving cores they never touch) and
+under-provisioned ones (running hot against their limits).
+
+Usage is summed across all containers in a pod; only `Running` pods are shown.
+Reads live data from the `metrics.k8s.io` API (same source as `kubectl top`).
+
+## Build
+
+```sh
+make podgap          # from the repo root → ./bin/podgap
+# or: go build -o podgap ./podgap
+```
+
+## Usage
+
+```sh
+podgap                       # live TUI, all namespaces, refresh every 3s
+podgap --top 15 -i 5s        # top 15 by CPU waste, refresh every 5s
+podgap -n observability -s mem-util
+podgap --over                # over-provisioned pods (right-size DOWN candidates)
+podgap --under               # usage over request or near limit (right-size UP)
+podgap -o json               # one-shot machine output (no TUI); also -o csv
+```
+
+### Keys
+
+| Key | Action |
+|-----|--------|
+| `↑`/`↓`, `j`/`k` | Scroll |
+| `pgup`/`pgdn`, `g`/`G` | Page / jump to top/bottom |
+| `c` / `C` | Sort by CPU waste / CPU utilization |
+| `m` / `M` | Sort by memory waste / memory utilization |
+| `n` | Sort by name |
+| `p` / `space` | Pause / resume auto-refresh |
+| `r` | Refresh now |
+| `q` / `esc` | Quit |
+
+### Reading the table
+
+```
+NAMESPACE  POD  CPU req→use/lim  ▲  CPU%  MEM req→use/lim  ▲  MEM%  CPU wst  MEM wst
+```
+
+- **req→use/lim** — configured request, live usage, configured limit (`-` if unset).
+- **▲ / ▼ / ·** — usage rose / fell / held steady since the last refresh.
+- **CPU% / MEM%** — usage as a percentage of the *request*; tinted amber ≥80%,
+  red ≥100% (`n/a` if no request set).
+- **wst** (waste) — `request − usage`. Positive = idle reserved capacity;
+  negative = over the request (a right-size-*up* candidate).
+
+## Flags
+
+| Flag | Default | Description |
+|------|---------|-------------|
+| `-n, --namespace` | all | Namespace to inspect |
+| `-s, --sort` | `cpu-waste` | `cpu-waste`, `mem-waste`, `cpu-util`, `mem-util`, `cpu-use`, `mem-use`, `name` |
+| `--top` | `0` (all) | Show only the top N rows |
+| `-i, --interval` | `3s` | TUI refresh interval |
+| `-o, --output` | `tui` | `tui`, `json`, `csv` |
+| `--over` | off | Only over-provisioned pods (util < `--threshold`) |
+| `--under` | off | Only under-provisioned pods |
+| `--threshold` | `0.5` | Utilization fraction defining "over-provisioned" |
+| `--kubeconfig` | — | Path to kubeconfig (default: in-cluster, then `$KUBECONFIG`, then `~/.kube/config`) |
+
+## Requirements
+
+- A cluster with metrics-server / the `metrics.k8s.io/v1beta1` API (check with
+  `kubectl top pods`).
+- RBAC: `list` on `pods` and on `pods.metrics.k8s.io`.