- set -euo pipefail with audit: every tolerated failure is guarded
- write --theme to bat's config file, not into the themes/ directory (was: append to a directory, failed silently)
- download and configure the same theme (Catppuccin Mocha; was: Macchiato downloaded, Mocha configured)
- preserve MANPAGER quoting via printf (was: collapsed to export MANPAGER=bat -plman, invalid when sourced)
- detect shell via $SHELL instead of $0 (was: always matched *) and reported 'Unsupported shell: bat.sh')
- fish branch appends fish syntax, no more exec of a mangled command string
- check pacman/apt bat install results (was: unchecked, continued on failure)
- idempotent appends (grep guard), tty-guarded fish warning
- remove broken rc-sourcing block (sourced .zshrc/config.fish from bash)