Implement magic bitboards for sliding piece move generation

[sbesselsen]

Replace the manual ray-casting implementation for rooks, bishops, and queens
with O(1) magic bitboard lookups. This uses precomputed lookup tables indexed
by a "magic" hash of the occupancy on relevant squares, similar to Stockfish's
approach.

Key changes:

• Add magic.rs module with lazy-initialized lookup tables using OnceLock
• Use proven magic numbers from Stockfish for both rooks and bishops
• Simplify rooklike_moves_masks and bishoplike_moves_masks in board.rs
• Handle board's inverted bit indexing at the interface

All perft tests pass with correct results.