docs site: rewrite directory-style links to their landing pages

A MkDocs hook turns links like [incidents/](incidents/) — which Gitea
renders as a directory listing but a static site would resolve against the
page URL — into links to the generated landing page for that directory.

mkdocs.yml

@@ -87,6 +87,11 @@ plugins:
   # Built-in, offline search — the index is a JSON file in the build output.
   - search
 
+hooks:
+  # Rewrites directory-style links (e.g. [incidents/](incidents/)) to the
+  # landing pages the build generates for them. Publishing-layer logic only.
+  - publishing/hooks.py
+
 markdown_extensions:
   - admonition
   - attr_list