A slideshow across a page: pictures the full width of the screen, captions over them

slideshow on a page: max_height in svh, slides with an image (a path
in the content repo or https), a caption laid over the picture's foot,
and optionally the picture's size so its place is held before it
loads. Swiper upgrades it; before that it is a row that scrolls.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GT37Z1Xtfd9pUuQtMTg6Yt

docs/content-reference.md

@@ -76,6 +76,26 @@ nearest `_section.yaml`. `event` makes a page an occasion with a time;
 opening any `type: location` field on the page there rather than on
 the whole world.
 
+### Pictures across the page
+
+`slideshow` lays a strip of pictures under the question, the full
+width of the screen: every picture as tall as the strip and as wide as
+its own shape, swiped or arrowed through, its caption over its foot.
+
+```yaml
+slideshow:
+  max_height: 60               # svh; 60 unless set, between 20 and 100
+  slides:
+    - image: images/built/01.webp     # a path in the content repo, or https://
+      caption: The canteen at the theatre, renewed
+      width: 3207                     # the picture's own size, optional:
+      height: 1400                    # holds its place before it has loaded
+```
+
+Pictures in the content repo are served from this origin under
+`/site/`; `webp`, `avif` and `jpeg` may be kept by the browser for an
+hour. Keep them web-sized: around 1400 pixels tall is plenty.
+
 ## An alternative
 
 One choice. Never two actions behind one heading: if two things can be