Beets shouldn't colorize (at least by default) if output is to a file or pipe rather than a tty.

### Problem

This will output bad files to "bad-mp3.txt" but will also include ansi escape sequences which makes the file hard to read.

```sh
beet bad format:mp3 | tee bad-mp3.txt
```

ideally, beets shouldn't colorize (at least by default) if output is to a file or pipe rather than a tty.

Start by reproducing the issue with `beet bad format:mp3 | tee bad-mp3.txt` and trace the CLI's colorization behavior for terminal versus piped output. Done means piped or redirected output has no ANSI escape sequences by default while interactive terminal output retains its existing behavior; add coverage for both cases.

Written by the indexing model from the issue text.