Add TTY detection to automatically disable ANSI colors when stdout is
piped or redirected. Respects standard conventions:
- NO_COLOR environment variable (no-color.org)
- CLICOLOR=0 disables color
- CLICOLOR_FORCE enables color even in non-TTY
Also adds ShouldUseEmoji() helper controlled by BD_NO_EMOJI.
Pager already disabled non-TTY in previous work (bd-jdz3).
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
