docs: clarify Python module responsibilities

Rewrite the module-level descriptions for all 28 Python files and remove the obsolete integration note from grok_register_ttk.py. Verified on Python 3.9 and Python 3.12.

tests/test_cpa_core.py

@@ -1,3 +1,5 @@
+"""验证 CPA 凭证结构、写入和核心 mint 流程。"""
+
 import tempfile
 import unittest
 from pathlib import Path