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, 1 insertions, 1 deletions

diff --git a/internal/web/templates/partials/mdhelp.html b/internal/web/templates/partials/mdhelp.html
index 5489510..cbf9b02 100644
--- a/internal/web/templates/partials/mdhelp.html
+++ b/internal/web/templates/partials/mdhelp.html
@@ -5,5 +5,5 @@
     <tr><td><code>[{{t "link text"}}](https://example.org)</code></td><td><code>![{{t "description"}}](/media/…)</code>, <code>[{{t "file name"}}](/media/…)</code> — <em>{{t "Insert file"}}</em> {{t "writes this for you"}}</td></tr>
     <tr><td><code>- {{t "list item"}}</code> / <code>1. {{t "numbered"}}</code></td><td><code>&gt; {{t "quote"}}</code>, <code>`{{t "code"}}`</code>, <code>---</code> {{t "for a line"}}</td></tr>
   </table>
-  <p class="muted small">{{t "Blank line = new paragraph. Press Enter once for a line break."}}</p>
+  <p class="muted small">{{t "Blank line = new paragraph. Press Enter once for a line break."}} {{t "A line with"}} <code>&lt;!--more--&gt;</code> {{t "marks where the summary ends on listings that show one."}}</p>
 </details>{{end}}