Function format_tier_bullet 

pub fn format_tier_bullet(
    label: &str,
    count: usize,
    tier: ConfidenceTier,
    color: bool,
) -> String

Format a confidence tier bullet.

• ● (filled circle) for high confidence (> 85%)
• ◐ (half circle) for medium confidence (50–85%)
• ○ (empty circle) for low confidence (< 50%)

Returns: ● High (12) or ◐ Medium (5) etc.