docs(CHANGES) sphinx-gp-opengraph and sphinx-gp-sitemap, with brief subsections

why: after the filter-repo sweep collapsed the gp-* → sphinx-gp-*
rename across the entire branch history, the Features section had
three multi-paragraph bullets describing the new packages plus the
gp-sphinx auto-wiring. Replace them with three brief #### subsections
that describe the shipped surface in two sentences each, name the
renamed packages, and carry the (#22) PR ref.

what:
- CHANGES: replace the three SEO Features bullets with three ####
  subsections — "New package: sphinx-gp-opengraph", "New package:
  sphinx-gp-sitemap", and "gp-sphinx: SEO config auto-wired from
  docs_url" — each ~3 lines, with (#22) PR refs
- uv.lock: refresh certifi (incidental)

Author: tony

CHANGES

@@ -31,25 +31,25 @@ $ uv add gp-sphinx --prerelease allow
 
 ### Features
 
-- `sphinx-gp-opengraph`: new workspace package providing OpenGraph and Twitter
-  meta-tag emission for Sphinx. Drop-in replacement for the
-  transitive `sphinxext-opengraph` dep — same `ogp_*` configuration
-  surface, minus the matplotlib-based social-card generator (which is
-  accepted but ignored, with a one-line warning pointing at the
-  static-image workflow). Replaces `sphinxext.opengraph` in
-  `DEFAULT_EXTENSIONS`.
-- `sphinx-gp-sitemap`: new workspace package providing `sitemap.xml`
-  generation for Sphinx. Added to `DEFAULT_EXTENSIONS` so every
-  gp-sphinx site gets a sitemap out of the box. Drop-in replacement
-  for the standalone `sphinx-sitemap` package with three Sphinx 8.1+
-  modernizations: plain `env.temp_data` list instead of
-  `multiprocessing.Queue`, `app.builder.name == "dirhtml"` instead of
-  an `env.is_directory_builder` monkey-patch, and
-  `contextlib.suppress(ExtensionError)` instead of a bare
-  `except BaseException`.
-- `gp-sphinx`: `merge_sphinx_config` auto-wires `site_url` (for
-  `sphinx-gp-sitemap`) from `docs_url`, alongside the existing
-  `ogp_site_url` / `ogp_site_name` / `ogp_image` auto-wiring.
+#### New package: `sphinx-gp-opengraph`
+
+OpenGraph meta-tag emission. Drop-in for `sphinxext-opengraph`,
+matplotlib-free; `ogp_social_cards` is accepted but ignored with a
+warning. Replaces `sphinxext.opengraph` in `DEFAULT_EXTENSIONS`.
+(#22)
+
+#### New package: `sphinx-gp-sitemap`
+
+`sitemap.xml` generator. Drop-in for `sphinx-sitemap` with Sphinx
+8.1+ idioms — no `multiprocessing.Queue`, public `dirhtml` detection,
+narrow `ExtensionError` handling. Added to `DEFAULT_EXTENSIONS`.
+(#22)
+
+#### `gp-sphinx`: SEO config auto-wired from `docs_url`
+
+`merge_sphinx_config` auto-derives `ogp_site_url`, `ogp_site_name`,
+`ogp_image`, `site_url`, and `sitemap_url_scheme` (flat `"{link}"`)
+from a single `docs_url`. (#22)
 - `sphinx-gp-theme`: dispatch `gp-sphinx:navigated` CustomEvent on
   `document` after every SPA-nav DOM swap. Third-party widgets that bind to
   swapped DOM can listen for this event to re-initialise after navigation