Fix broken canonical URLs in the example gallery (#893)

* Fix canonical URLs and stale blog base URL

html_baseurl was missing the /en/latest/ segment, so the canonical URL
Sphinx writes into every page pointed at a URL that redirects to a 404.
Old versioned builds therefore keep competing with latest in search
engines instead of transferring their ranking.

Sitemap URLs are unchanged: the version prefix moves from
sitemap_url_scheme into the base URL.

Also point blog_baseurl at www.pymc.io instead of the old docs.pymc.io
domain.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Give the gallery page a real meta description and intro

The generated gallery.rst had no description, so search engines built
the snippet from concatenated card titles ('Introductory: General
Overview Introductory Overview of PyMC Simple Linear Regression...').
The gallery page has 269k search impressions at 1.3% CTR.

Add an explicit meta description plus a one-sentence visible intro.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: twiecki

examples/conf.py

@@ -71,9 +71,11 @@ def setup(app: Sphinx):
 
 # theme options
 html_theme = "pymc_sphinx_theme"
-html_baseurl = "https://www.pymc.io/projects/examples/"
+# Also used to build each page's canonical URL, so it points at the default
+# (latest) version: <html_baseurl> + <page name>.html
+html_baseurl = "https://www.pymc.io/projects/examples/en/latest/"
 rtd_version = os.environ.get("READTHEDOCS_VERSION", "")
-sitemap_url_scheme = f"{{lang}}{rtd_version}/{{link}}"
+sitemap_url_scheme = "{link}"
 html_theme_options = {
     "secondary_sidebar_items": ["postcard", "page-toc", "edit-this-page", "sourcelink", "donate"],
     "navbar_start": ["navbar-logo"],
@@ -127,7 +129,7 @@ def setup(app: Sphinx):
 }
 
 # ablog config
-blog_baseurl = "https://docs.pymc.io/projects/examples/en/latest/"
+blog_baseurl = "https://www.pymc.io/projects/examples/en/latest/"
 blog_title = "PyMC Examples"
 blog_path = "blog"
 blog_authors = {

sphinxext/thumbnail_extractor.py

@@ -28,6 +28,14 @@
 PyMC Example Gallery
 ====================
 
+.. meta::
+   :description: Hundreds of runnable PyMC example notebooks: regression,
+       hierarchical models, Gaussian processes, time series, causal
+       inference, and more Bayesian modeling recipes.
+
+A collection of runnable Jupyter notebooks showing how to solve real modeling
+problems with PyMC, from simple regression to advanced Bayesian workflows.
+
 .. toctree::
    :hidden: