attackers_to(square, by_color)

[Hardcode3]

🎯 Goal

Efficiently answer:

“Which pieces attack this square?”

🧠 Key Idea

Use reverse attacks from the target square.

🛠️ Tasks

Implement attackers for:

• pawns (reverse direction)

• knights

• king

• bishops / queens

• rooks / queens

• Return a Bitboard of attacking pieces

✅ Acceptance Criteria

• Unit tests on known positions
• Used for check detection and castling validation