fix: break automatically when all trees have composted

src/bin/ponderosa-cpu.rs

@@ -144,6 +144,10 @@ fn main() -> io::Result<()> {
             break;
         }
 
+        if scheduled_trees.len() == 0 {
+            break;
+        }
+
         let mut trees_to_plant: Vec<state::Tree> = Vec::new();
         let mut rules_to_define: Vec<state::Rule> = Vec::new();
         let mut trees_to_wake: Vec<u16> = Vec::new();