Problem

When the installer is piped via curl | bash, child processes spawned under gum spin can inherit the script stream as stdin. Gum v0.17.0 sets the wrapped command's stdin to os.Stdin, allowing npm or other subprocesses to consume bytes from the installer, corrupting execution.

Additionally, fallback paths redirect stdin unconditionally from /dev/null, breaking interactive commands like Homebrew installation prompts when the script is run directly (bash install.sh).

Expected behavior

• Piped mode (curl | bash): child processes should not be able to read from the piped script stream
• Direct mode (bash install.sh): interactive commands should retain terminal stdin for user prompts

Actual behavior

• Piped mode: gum-wrapped child commands inherit the piped script stream as stdin
• Direct mode: fallback paths unconditionally redirect stdin from /dev/null, breaking interactive prompts

Affected files

• scripts/install.sh (run_with_spinner, run_quiet_step, run_npm_global_install)