feat: dungeon generation — BSP rooms, room types, fog of war

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

dungeon/fov.go

@@ -0,0 +1,27 @@
+package dungeon
+
+type Visibility int
+
+const (
+	Hidden  Visibility = iota
+	Visited
+	Visible
+)
+
+func UpdateVisibility(floor *Floor) {
+	for i, room := range floor.Rooms {
+		if i == floor.CurrentRoom {
+			room.Visited = true
+		}
+	}
+}
+
+func GetRoomVisibility(floor *Floor, roomIdx int) Visibility {
+	if roomIdx == floor.CurrentRoom {
+		return Visible
+	}
+	if floor.Rooms[roomIdx].Visited {
+		return Visited
+	}
+	return Hidden
+}