Adds a new sphinx_runpython.runmermaid Sphinx extension exposing a .. runmermaid:: directive that renders Mermaid diagrams. The name runmermaid avoids conflicts with the existing sphinxcontrib-mermaid extension (which also registers .. mermaid::) and the mermaid-py Python package. HTML output is rendered client-side via the Mermaid CDN JS library; LaTeX/text/RST outputs fall back to verbatim source.

New extension: sphinx_runpython/runmermaid/

• RunMermaidDirective – .. runmermaid:: directive with:
  • :script: – body is Python code whose stdout is the diagram definition; an optional string value acts as a split token (only output after that token is used)
  • :process: – run the script in a subprocess
  • Result caching: identical scripts are not re-executed within a build
• Node visitors for HTML (<pre class="mermaid">), RST, text, and LaTeX
• add_mermaid_js – builder-inited hook that injects mermaid.min.js from CDN into HTML pages

Usage

.. runmermaid::

    graph LR
        A --> B --> C

.. runmermaid::
    :script: DIAGRAM

    print("DIAGRAM")
    print("graph LR\n    A --> B")

Supporting changes

• _doc/conf.py – extension registered as sphinx_runpython.runmermaid, Mermaid added to epkg_dictionary
• _doc/api/runmermaid.rst + _doc/api/index.rst – documentation page
• _unittests/ut_runmermaid/test_runmermaid_extension.py – 5 tests covering inline RST/HTML rendering, script execution, split-token filtering, and caching