Legal non-sliding moves (knights)

[Hardcode3]

🎯 Goal

Generate legal knight moves.

🧠 Key Idea

A pinned knight has zero legal moves.

🛠️ Tasks

• Skip knights in pinned
• Apply:
  • ~own_pieces
  • check_mask

✅ Acceptance Criteria

• Pinned knights generate no moves
• Free knights behave correctly