fix: composer superuser handling and unify warning tips

[rozsazoltan]

• Add COMPOSER_ALLOW_SUPERUSER=1 to Composer verification to prevent interactive prompts when running in elevated environments (e.g. containers, CI, or root).
• Standardize warning messages across the plugin with consistent 💡 tips to guide users on how to debug issues (e.g. using PHP_VERBOSE=1 or manual verification commands).
• Improve overall UX by making failures non-blocking where appropriate and surfacing actionable hints.