fix: pin Python API documentation build dependencies

.github/workflows/build_static_website.yml

@@ -40,7 +40,7 @@ jobs:
       - name: Install Dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install mkdocs-material 'mkdocstrings[python]' black
+          pip install -r api-reference/python-api/requirements.txt
           pip install zvec
           npm ci
 

.github/workflows/pr-preview-build.yml

@@ -42,7 +42,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install mkdocs-material 'mkdocstrings[python]' black
+          pip install -r api-reference/python-api/requirements.txt
           pip install zvec
           npm ci
 

api-reference/python-api/README.md

@@ -6,10 +6,10 @@ This is the official Python API reference documentation for the Zvec library, bu
 
 ### 1. Install Dependencies
 
+Run these commands from `api-reference/python-api`.
+
 ```bash
-pip install mkdocs-material
-pip install 'mkdocstrings[python]'
-pip install black
+pip install -r requirements.txt
 pip install zvec
 ```
 

api-reference/python-api/requirements.txt

@@ -0,0 +1,8 @@
+# Documentation tool versions from the successful PR build on 2026-09-23.
+mkdocs==1.6.1
+mkdocs-material==9.7.7
+mkdocstrings[python]==1.0.6
+mkdocstrings-python==2.0.9
+# 12.2+ requires a Markdown argument that mkdocstrings 1.0.6 does not pass.
+pymdown-extensions==12.1
+black==26.5.1