Nothing is selected as the current context - a fresh kubeconfig, or one where the selection was unset. kubectx -c has nothing to print, so it errors. Pick a context: run bare kubectx, choose one with kubectx [name], and kubectx -c prints it from then on.

## The error
```text
current-context is not set
```

## What to do
1. See the available contexts:
```bash
kubectx
```
   Expected: Lists the contexts in the file.
2. Select one:
```bash
kubectx [name]
```
   Expected: Prints `Switched to context "[name]".`.
3. Verify:
```bash
kubectx -c
```
   Expected: Prints the context name, exit 0.

## When this applies
- the exact current-context is not set message from kubectx -c / --current
- fresh kubeconfigs that define contexts but select none
- after kubectx -u unsets the context

## When it does NOT apply
- no context exists with the name (the name is wrong)
- every kubectl command failing (the whole config is missing)

## Works with
kubectx (ahmetb/kubectx)

### error: current-context is not set (kubectl config current-context)
kubectl's version of the same state. Same fix: use-context with a real name.

## Why it happens
current-context is just a field in the kubeconfig. Tools that merge or regenerate configs can leave it empty, and anything asking for the current selection then fails.

## Edge cases
- kubectx -u deliberately unsets the context - this error right after is expected, not a bug.
- Some automation unsets the context to force an explicit choice; set it once per shell instead.

## Resolved from
gh:nao1215/atago (e2e kubectx behavior spec) - https://github.com/nao1215/atago/blob/HEAD/doc/e2e/kubectx.md