fix(install): make setup failures explicit and atomic

Installer pipelines masked dependency and download failures, causing
false success messages and unsafe config replacement.

Atomic updates and current upstream installers keep failures visible.

install_pyenv.sh

@@ -1,7 +1,6 @@
 #!/bin/bash
 
-# Save the original working directory
-ORIGINAL_DIR="$(pwd)"
+set -euo pipefail
 
 # Install pyenv (Python Version Manager) if it is not already installed
 if command -v pyenv &> /dev/null; then
@@ -15,6 +14,7 @@ else
     export PYENV_ROOT="$HOME/.pyenv"
     [[ -d $PYENV_ROOT/bin ]] && export PATH="$PYENV_ROOT/bin:$PATH"
     eval "$(pyenv init - bash)"
+    command -v pyenv &> /dev/null
 fi
 
 # OPTIONAL: Install the latest stable version of Python
@@ -22,7 +22,4 @@ fi
 # pyenv install 3.12.0 && pyenv global 3.12.0
 
 # Apply the pyenv zsh configuration patch (downloads zshrc/pyenv.zsh to ~/.config/zshrc/pyenv.zsh)
-curl -s https://git.miomio.moe/mio/easyzsh/raw/branch/master/patch.sh | bash -s pyenv
-
-# Restore original working directory
-cd "$ORIGINAL_DIR"
+curl -fsSL https://git.miomio.moe/mio/easyzsh/raw/branch/master/patch.sh | bash -s -- pyenv