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_nvm.sh

@@ -1,7 +1,9 @@
 #!/bin/bash
 
-# Save the original working directory
-ORIGINAL_DIR="$(pwd)"
+set -euo pipefail
+
+NVM_VERSION="v0.40.4"
+export NVM_DIR="${NVM_DIR:-$HOME/.nvm}"
 
 # Install nvm (Node Version Manager) if it is not already installed
 if command -v nvm &> /dev/null; then
@@ -9,19 +11,15 @@ if command -v nvm &> /dev/null; then
 else
     echo -e "Installing nvm (Node Version Manager)\n"
     # Using the official install script (https://github.com/nvm-sh/nvm)
-    curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | bash
+    curl -fsSL "https://raw.githubusercontent.com/nvm-sh/nvm/${NVM_VERSION}/install.sh" | bash
 
     # Load nvm for the remainder of this script
-    export NVM_DIR="${XDG_CONFIG_HOME:-$HOME/.nvm}"
     [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"
+    command -v nvm &> /dev/null
 fi
 
-# OPTIONAL: Install the latest LTS version of Node.js
-# Uncomment the following line if you would like to automatically install it
+# Install the latest LTS version of Node.js
 nvm install --lts
 
-# Apply the "basic" zsh configuration patch (downloads zshrc/basic.zsh to ~/.config/zshrc/basic.zsh)
-curl -s https://git.miomio.moe/mio/easyzsh/raw/branch/master/patch.sh | bash -s nvm
-
-# Restore original working directory
-cd "$ORIGINAL_DIR"
+# Apply the nvm zsh configuration patch
+curl -fsSL https://git.miomio.moe/mio/easyzsh/raw/branch/master/patch.sh | bash -s -- nvm