feat(core): add move encoding and move list

Move.scala

@@ -0,0 +1,60 @@
+package gambit
+
+object Move:
+  private val ToShift = 7
+  private val PromoShift = 14
+  private val CaptureBit = 1 << 17
+  private val EnPassantBit = 1 << 18
+  private val DoubleBit = 1 << 19
+  private val CastleBit = 1 << 20
+
+  def make(
+      from: Int,
+      to: Int,
+      promo: Int = 0,
+      capture: Boolean = false,
+      enPassant: Boolean = false,
+      double: Boolean = false,
+      castle: Boolean = false
+  ): Int =
+    from |
+      (to << ToShift) |
+      (promo << PromoShift) |
+      (if capture then CaptureBit else 0) |
+      (if enPassant then EnPassantBit else 0) |
+      (if double then DoubleBit else 0) |
+      (if castle then CastleBit else 0)
+
+  inline def from(m: Int): Int = m & 0x7f
+  inline def to(m: Int): Int = (m >> ToShift) & 0x7f
+  inline def promo(m: Int): Int = (m >> PromoShift) & 7
+  inline def isCapture(m: Int): Boolean = (m & CaptureBit) != 0
+  inline def isEnPassant(m: Int): Boolean = (m & EnPassantBit) != 0
+  inline def isDouble(m: Int): Boolean = (m & DoubleBit) != 0
+  inline def isCastle(m: Int): Boolean = (m & CastleBit) != 0
+  inline def isPromotion(m: Int): Boolean = promo(m) != 0
+
+  def uci(m: Int): String =
+    val base = Square.name(from(m)) + Square.name(to(m))
+    if isPromotion(m) then base + promoChar(promo(m)) else base
+
+  private def promoChar(t: Int): String = t match
+    case Piece.Knight => "n"
+    case Piece.Bishop => "b"
+    case Piece.Rook   => "r"
+    case Piece.Queen  => "q"
+    case _            => ""
+
+final class MoveList(capacity: Int = 256):
+  private val data = new Array[Int](capacity)
+  var size = 0
+
+  def add(m: Int): Unit =
+    data(size) = m
+    size += 1
+
+  def apply(i: Int): Int = data(i)
+
+  def update(i: Int, m: Int): Unit = data(i) = m
+
+  def clear(): Unit = size = 0