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.

cpa_xai/mint.py

@@ -1,4 +1,4 @@
-"""High-level OIDC mint + export pipeline."""
+"""协调浏览器授权、OAuth 轮询和 CPA 凭证导出流程。"""
 
 from .browser_confirm import mint_with_browser
 from .schema import DEFAULT_BASE_URL, build_cpa_xai_auth