style: align Starship colors with terminal palette

[jiminu]

Summary

• use terminal ANSI colors so the prompt follows the active terminal theme
• align Git status colors with Git conventions and reserve bold for important states
• compact status counts and visually separate worktree state from ahead/behind state

Verification

• bash scripts/check.sh
• Starship 1.26.0 prompt/module render smoke checks
• git diff --check