feat: add Chapter 2 gold miner FSM example in Go

Port the finite state machine from "Programming Game AI by Example"
chapter 2: BaseGameEntity, a generic State[T]/StateMachine[T] pair
(Go generics standing in for the book's C++ templates), and a Miner
that cycles through digging, banking, sleeping, and drinking states.
VisitBankAndDepositGold, GoHomeAndSleepTilRested, and QuenchThirst
are original implementations based on the book's written behavior
description, since their C++ source wasn't available. Includes a
runnable demo in main.go.

chapter-2-state-driven-agent-design/westworld/names.go

@@ -0,0 +1,20 @@
+package westworld
+
+import "fmt"
+
+// entityNames is a temporary stand-in for the book's real name
+// lookup table. We still haven't been shown that table, so this is
+// just a small map we're filling in by hand as we meet entities -
+// right now that's only the miner from main.go, whose ID is 1.
+var entityNames = map[int]string{
+	1: "Miner Bob",
+}
+
+// GetNameOfEntity looks up a friendly name for a given entity ID.
+// Anything not in entityNames falls back to printing the raw ID.
+func GetNameOfEntity(id int) string {
+	if name, ok := entityNames[id]; ok {
+		return name
+	}
+	return fmt.Sprintf("Entity %d", id)
+}