[Code scan] docs/index.rst references a missing intro document

[njzjz]

This issue was found by a Codex global code scan of the repository.

Affected code:

dargs/docs/index.rst

Lines 9 to 21 in b4db564

	.. toctree::
	:maxdepth: 2
	:caption: Contents:
	intro
	cli
	sphinx
	dpgui
	nb
	json_schema
	ref
	api/api
	credits

Problem:
The documentation toctree includes intro, but the repository does not contain docs/intro.rst or docs/intro.md.

Observed behavior:
The file list contains docs/index.rst, docs/cli.rst, docs/sphinx.rst, docs/dpgui.rst, docs/nb.ipynb, docs/json_schema.md, docs/ref.md, and docs/credits.rst, but no intro document. Sphinx will warn that the toctree references a nonexisting document, and warning-as-error builds will fail.

Expected behavior:
Either add the missing introduction document or remove/replace the intro toctree entry.