Install basic CLI tools (git curl wget + nslookup/kubectl) and document chmod

- ESSENTIAL now includes wget.
- Add best-effort CLI tools: htop, fzf, nslookup (dnsutils on Debian,
  bind-tools on Alpine).
- Attempt kubectl only when its package is available in the repos
  (not in default Debian/Alpine repos; install manually otherwise).
- README: add 'chmod +x install.sh' and a single-line
  clone+install+remove one-liner.

README.md

@@ -37,12 +37,20 @@ These are intentionally excluded from the repo:
 ```sh
 git clone git@git.ivanch.me:ivanch/dotfiles.git
 cd dotfiles
+chmod +x install.sh
 ./install.sh            # detects Debian/Alpine, installs pkgs + oh-my-zsh,
                         # deploys servers/ and installs Vim plugins
 # optional: ./install.sh --chsh   (set login shell to zsh)
 #           ./install.sh --dry-run (preview only)
 ```
 
+Or as a single line (clone, install, then remove the folder):
+
+```sh
+git clone git@git.ivanch.me:ivanch/dotfiles.git /tmp/dotfiles && \
+  cd /tmp/dotfiles && chmod +x install.sh && ./install.sh; cd /tmp && rm -rf /tmp/dotfiles
+```
+
 The installer:
 
 1. Detects the OS / package manager (`apt` on Debian, `apk` on Alpine) and