feat(kubernetes): Guard kubectl initialization and completions

Ensures kubectl-related aliases and functions are only sourced if the `kubectl` command is available.

bashrc_overrides/kubernetes

@@ -1,3 +1,4 @@
+if command -v kubectl >/dev/null 2>&1; then
   source <(kubectl completion bash)
   alias k="kubectl"
   alias kcontext="kubectl config use-context"
@@ -23,3 +24,4 @@ _kcontext_completion() {
   complete -F __start_kubectl k
   complete -F _kns_completion kns
   complete -F _kcontext_completion kcontext
+fi