fix(felling): support copper axes

src/main/java/games/dmg/treefeller/TreeTools.java

@@ -9,6 +9,7 @@ public final class TreeTools {
     private static final Set<Material> AXES = EnumSet.of(
             Material.WOODEN_AXE,
             Material.STONE_AXE,
+            Material.COPPER_AXE,
             Material.IRON_AXE,
             Material.GOLDEN_AXE,
             Material.DIAMOND_AXE,

src/test/java/games/dmg/treefeller/TreeFellingListenerTest.java

@@ -35,7 +35,7 @@ class TreeFellingListenerTest {
         when(player.getName()).thenReturn("Player");
         when(player.getGameMode()).thenReturn(GameMode.SURVIVAL);
         when(player.getInventory()).thenReturn(inventory);
-        when(inventory.getItemInMainHand()).thenReturn(new ItemStack(Material.IRON_AXE));
+        when(inventory.getItemInMainHand()).thenReturn(new ItemStack(Material.COPPER_AXE));
         TreeStructure tree = new TreeStructure(
                 TreeSpecies.OAK, List.of(new BlockPoint(0, 0, 0), new BlockPoint(0, 1, 0)));
         PlayerTreeFellerState eligible = PlayerTreeFellerState.initial(playerId, "Player")

src/test/java/games/dmg/treefeller/TreeToolsTest.java

@@ -11,6 +11,7 @@ class TreeToolsTest {
     void acceptsAxesButNotPickaxesOrOtherItems() {
         assertTrue(TreeTools.isAxe(Material.WOODEN_AXE));
         assertTrue(TreeTools.isAxe(Material.GOLDEN_AXE));
+        assertTrue(TreeTools.isAxe(Material.COPPER_AXE));
         assertTrue(TreeTools.isAxe(Material.NETHERITE_AXE));
         assertFalse(TreeTools.isAxe(Material.DIAMOND_PICKAXE));
         assertFalse(TreeTools.isAxe(Material.AIR));