Add post summaries, featured images and a page outro

Recreating gizmolab.net as a blog showed three things the design system
could not express, all of them ordinary blog features:

- Listings can show a summary and a "Read more" link instead of the whole
  post (theme.list_style). The summary is the source up to <!--more-->;
  without the marker a Markdown post is cut at a block boundary after 70
  words (never inside a code fence) and an HTML post is shown whole, since
  cutting hand-written markup blind would leave tags open. Computed at
  render time (Post.Excerpt/HasMore), nothing new is stored.
- A post can carry a featured image (posts.image, a library file that is
  unset when the file is deleted): a thumbnail floated beside the entry on
  listings, and on the post page above or below the text, or not at all,
  as theme.post_image says. The picker is the design page's imagepick; its
  library panel moves out of design.html into partials/imagelib.html so
  both forms share it — which also removes a stale pickAction call the
  design form's click handler would have hit.
- A page can have a closing text after its posts (pages.outro_md/html), in
  the intro's format: the per-page counterpart of the blog-wide "after the
  posts" module, for a home page that ends in a site map or a widget. The
  editor partial takes formatof to share another editor's Format row, and
  its upload field is now <name>_file so two editors fit in one form.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sd8UPWrvyYCLj97JexNw3A

1 files changed, 7 insertions, 3 deletions

diff --git a/README.md b/README.md
index 6b30fdc..90dca7a 100644
--- a/README.md
+++ b/README.md
@@ -16,9 +16,11 @@ Server-rendered HTML, no JavaScript required, works on old browsers and phones.
   the superadmin can set a different limit per blog.
 - **Announcements**: blog-wide notices (next meeting, this month's book, a closure)
   shown at the top or bottom of the main content or of a side column; each can be hidden without deleting.
-- Every blog has **pages** (Home, About, News, …); each page holds posts. Posts can
+- Every blog has **pages** (Home, About, News, …); each page holds posts, with an
+  optional text before them (an intro) and after them (a site map, a widget). Posts can
   carry **tags**, shown under the date; each tag has its own page listing every post
-  with it.
+  with it. A post can have a **featured image**: a thumbnail beside it on listings,
+  and the picture above or below the text on its own page.
 - **Design** tab: one form, one Save, organised by part of the blog — colours & fonts
   (schemes, background colour/image, text and link colours, fonts), header, menu,
   content, side columns, footer, logo & site icon. The page is five areas — header,
@@ -28,7 +30,9 @@ Server-rendered HTML, no JavaScript required, works on old browsers and phones.
   case; several words match in order with anything in between), custom HTML, footer
   text, RSS link, site map. Column widths are percentages; on phones the columns
   stack under the posts. The **menu** mixes blog pages and outside links. Posts per
-  page, the date format, the site title size and the footer alignment live here too.
+  page, the date format, the site title size and the footer alignment live here too,
+  as does whether listings show whole posts or **summaries** with a "Read more" link
+  (a post's summary ends at a `<!--more-->` line, or after its first paragraphs).
 - Changes are live once saved: save, then refresh the blog tab. Nothing is saved
   until you press Save, and Discard changes forgets the edits.
 - **Languages**: English or Greek, chosen per blog on the Settings tab. It switches the