Rename combat methods; -1 status codes become named bool results

Refactor step 5, combat: rollEm→rollAttacks; attack, moveMonster, and
chaseStep return (removed bool) instead of the C -1/0 int codes.
Behavior unchanged; suite green.

game/fight_test.go

@@ -32,7 +32,7 @@ func TestRollEmParsesMultiAttackDice(t *testing.T) {
 	// With attacker level 20 vs armor 10, swing always hits
 	// (rnd(20)+wplus >= (20-20)-10 is always true), so three attacks of
 	// 1x4 + str bonus 1 each must deal between 6 and 15 damage.
-	if !g.rollEm(att, def, nil, false) {
+	if !g.rollAttacks(att, def, nil, false) {
 		t.Fatal("attack with guaranteed swing missed")
 	}