- AMD: download directly to "$microcode" instead of a convoluted, unquoted
basename of the full URL (fixes ShellCheck SC2046) and pin to https.
- Quote dpkg install and cleanup paths (SC2086) and use rm -f.
- Normalize the Debian pool URLs (drop the stray double/triple slashes).
- Define color variables directly instead of via $(echo ...) (SC2116/SC2028).