missing option to force multi-column output

- os: MacOS
- `lsd --version`: lsd 1.0.0
- `echo $TERM`: xterm-kittyCO
- `echo $LS_COLORS`: di=1;36:ln=35:so=32:pi=33:ex=31:bd=34;46:cd=34;43:su=30;41:sg=30;46:tw=30;42:ow=30;43

## Expected behavior
In classic ls there is an option (-C) to force multi-column output.

## Actual behavior
In lsd multi-column output is the default when output is to a terminal, but when lsd is used in external program (like fzf) shows results in a single vertical column.

Would be nice to have an option like the classic ls one.

Start by tracing lsd's command-line option handling and output layout behavior, then compare the requested -C behavior with classic ls when output is piped to fzf. Done means a documented option reliably forces multi-column output outside an interactive terminal, with appropriate coverage for terminal and external-program use.

Written by the indexing model from the issue text.