docs site: generate landing pages for documented directories

infrastructure.md links to incidents/ the way Gitea renders directories.
A static site has no directory listing, so the build now generates a small
landing page (with each document's own title) for any documented directory
that lacks an index. Build artifact only — no document is touched.

publishing/build.sh

@@ -44,6 +44,29 @@ tar cf - \
 # A file that must sit at the site root (crawler rules), not under publishing/.
 cp publishing/robots.txt "$SITE_SRC/robots.txt"
 
+# The documents sometimes link to a directory (`incidents/`) the way Gitea
+# renders it. A static site has no directory listing, so generate a small
+# index page for any documented subdirectory that lacks one. This is a build
+# artifact — the documents themselves are never touched.
+(cd "$SITE_SRC" && find . -mindepth 1 -type d ! -path './publishing*' | while read -r dir; do
+  if compgen -G "$dir"/*.md >/dev/null && [ ! -f "$dir/index.md" ]; then
+    dir_name="$(basename "$dir")"
+    title="$(echo "$dir_name" | sed 's/-/ /g' | sed 's/^./\u&/')"
+    {
+      echo "# $title"
+      echo
+      echo "Landing page for this directory, generated by the publishing layer — the"
+      echo "documents themselves live untouched in the repository."
+      echo
+      for f in "$dir"/*.md; do
+        [ "$(basename "$f")" = "index.md" ] && continue
+        heading="$(grep -m1 '^# ' "$f" | sed 's/^# //' || true)"
+        echo "- [${heading:-$(basename "$f" .md)}]($(basename "$f"))"
+      done
+    } > "$dir/index.md"
+  fi
+done)
+
 # 2. Build.
 if [ ! -x "$VENV/bin/mkdocs" ]; then
   echo "Creating build venv at $VENV"