Add a centralized color module (cli/src/color.rs) that respects the NO_COLOR environment variable per https://no-color.org/ Changes: - Add color.rs module with helper functions for colored output - Refactor all hardcoded ANSI escape codes to use the color module - Add tests for color formatting functions - Update AGENTS.md with color module usage guidelines Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>