docs: move detailed script usage to doc/user-guide/scripts.md

Extract the verbose "Detailed Script Usage" section from both README.md
and README_zh.md into standalone reference pages at
doc/user-guide/scripts.md and doc/user-guide/scripts.zh.md.

Replace removed content with a one-line summary and a link to the new
pages. Register both new pages in mkdocs.yml navigation (EN + ZH).

Made-with: Cursor

Author: lixin0304