The script uses associative arrays (declare -A) which require Bash 4+.
macOS ships with Bash 3.2 due to GPLv3 licensing, causing the script to
fail with "declare: -A: invalid option". This adds a version check with
a helpful error message directing macOS users to install Bash via Homebrew.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>