fix: eliminate all ROOM_SIZE-related literals

Less buggy if we avoid literals and use the constant everywhere.

src/local/room_coordinate.rs

@@ -245,7 +245,7 @@ mod test {
         }
         base.iter()
             .copied()
-            .zip(1..51)
+            .zip(1..(ROOM_SIZE + 1))
             .for_each(|(actual, expected)| assert_eq!(actual, expected));
     }
 
@@ -254,13 +254,13 @@ mod test {
         let mut base: Box<[u16; ROOM_AREA]> = Box::new([0; ROOM_AREA]);
         for i in 0..ROOM_USIZE {
             for j in 0..ROOM_USIZE {
-                base[i * ROOM_USIZE + j] = i as u16 * 50;
+                base[i * ROOM_USIZE + j] = i as u16 * ROOM_SIZE as u16;
             }
         }
 
         for i in 0..ROOM_SIZE {
             let coord = RoomCoordinate::new(i).unwrap();
-            assert!(base[coord].iter().copied().all(|val| val == i as u16 * 50));
+            assert!(base[coord].iter().copied().all(|val| val == i as u16 * ROOM_SIZE as u16));
             for j in 0..ROOM_USIZE {
                 base[coord][j] += j as u16;
             }