Readme and comments and reward pdated

readme was outdated
env rewards got a penalty for standing still while it should move instead of 0 reward

ml/callbacks.py

@@ -1,6 +1,9 @@
 """
-ml/callbacks.py - Stable-Baselines3 Custom Callbacks for Logging & Curriculum Advancement
-Fully compatible with SubprocVecEnv and DummyVecEnv.
+ml/callbacks.py - Stable-Baselines3 callbacks for training diagnostics.
+
+These callbacks extend SB3 training with two responsibilities: logging reward-component
+statistics for TensorBoard/console output, and checking whether the curriculum should
+advance to a harder set of commands based on recent training performance.
 """
 
 import numpy as np