switch coordinates to global 'Coord' type

src/complexagent.rs

@@ -1,7 +1,7 @@
 use crate::{
     agent::Agent,
     logic::{FutureMoveConfig, FutureMoves},
-    repr::{Board, Piece},
+    repr::{Board, Coord, Piece},
 };
 
 pub struct ComplexAgent {
@@ -27,7 +27,7 @@ impl ComplexAgent {
 }
 
 impl Agent for ComplexAgent {
-    fn next_move(&mut self, board: &Board) -> Option<(usize, usize)> {
+    fn next_move(&mut self, board: &Board) -> Option<(Coord, Coord)> {
         self.future_moves.update_from_board(board);
 
         println!("# of moves stored: {}", self.future_moves.arena_len());