docs: switch docs to shibuya theme and install via venv

- change documentation theme from `alabaster` to `shibuya`
- add pinned Documentation requirements for `sphinx` and `shibuya`
- update workflows to create `.venv` and install with `requirements.txt`
- ignore common virtual environment directories (`.conda` and `.venv`)

.github/workflows/deploy_docs.yml

@@ -19,10 +19,15 @@ jobs:
     - name: Install dependencies
       run: |
         sudo apt update -qq
-        sudo apt install -y make autoconf python3-sphinx
+        sudo apt install -y make autoconf python3-venv
+        python3 -m venv .venv
+        . .venv/bin/activate
+        pip install --upgrade pip
+        pip install -r Documentation/requirements.txt
 
     - name: Make Documentation
       run: |
+        . .venv/bin/activate
         cd Documentation
         make html
 

.github/workflows/test.yml

@@ -54,7 +54,11 @@ jobs:
     - name: Install dependencies
       run: |
         sudo apt update -qq
-        sudo apt install -y make g++ git bison flex gperf libreadline-dev libbz2-dev autoconf python3-sphinx
+        sudo apt install -y make g++ git bison flex gperf libreadline-dev libbz2-dev autoconf python3-venv
+        python3 -m venv .venv
+        . .venv/bin/activate
+        pip install --upgrade pip
+        pip install -r Documentation/requirements.txt
 
     - name: Build, check and install
       run: |
@@ -69,6 +73,7 @@ jobs:
 
     - name: Documentation
       run: |
+        . .venv/bin/activate
         cd Documentation
         make html
 

.gitignore

@@ -8,6 +8,10 @@
 *.swp
 *~
 
+# Virtual environments
+.conda/
+.venv/
+
 # Top level generic files
 tags
 TAGS

Documentation/conf.py

@@ -76,7 +76,7 @@ highlight_language = 'none'
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
 #
-html_theme = 'alabaster'
+html_theme = 'shibuya'
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the

Documentation/requirements.txt

@@ -0,0 +1,2 @@
+sphinx==8.1.3
+shibuya==2026.1.9