Looking at all the files, I notice that you're using m2r2 to include …

…the README.md file in your documentation, and there's quite a bit of complex markdown content in both README files, including tables, mermaid diagrams, and relative image paths.

The error occurs when trying to parse this content. Let's try a few fixes:
First, update your conf.py to explicitly set markdown support:

docs/conf.py

@@ -36,6 +36,7 @@
     'numpydoc',
     'm2r2',
     'sphinxcontrib.mermaid',
+    'recommonmark',
     ]
 
 extlinks = {
@@ -70,6 +71,26 @@
     '.md': 'markdown',
 }
 
+# Configure m2r2
+source_parsers = {
+    '.md': 'm2r2.parser.MarkdownParser'
+}
+
+# Enable markdown support in RST
+extensions.append('recommonmark')
+
+# Configure recommonmark
+import recommonmark
+from recommonmark.transform import AutoStructify
+
+def setup(app):
+    app.add_config_value('recommonmark_config', {
+        'enable_eval_rst': True,
+        'enable_math': True,
+        'enable_inline_math': True,
+    }, True)
+    app.add_transform(AutoStructify)
+    app.connect('build-finished', copy_examples)
 
 # Copy ./examples/results images into documentation so they show up when
 # markdown files with relative paths are transcluded (suggested by ChatGPT-4)
@@ -84,7 +105,3 @@ def copy_examples(app, docname):
         if not os.path.exists(output_dir):
             os.makedirs(os.path.join(app.outdir, 'examples'))
             shutil.copytree(source_dir, output_dir)
-
-
-def setup(app):
-    app.connect('build-finished', copy_examples)

docs/requirements.txt

@@ -4,4 +4,5 @@ numpydoc
 m2r2
 sphinxcontrib.mermaid
 sphinx_rtd_theme
-sphinxcontrib-apidoc
+sphinxcontrib-apidoc
+recommonmark