Fix world briefing & add LLM enrichment, colophon fix, x4 cover fix

- World Briefing now starts with yesterday, preserves complete nested
event hierarchies and Wikipedia links, fetches deduplicated article
leads concurrently, and adds stable-ID summaries plus a daily overview.
- Enrichment runs after normal editorial work and degrades safely with
report warnings.
- Colophon facts now use X4-safe block paragraphs.
- Standard cover remains 1200×1600 RGB PNG.
- X4 cover is a 480×800 baseline RGB JPEG with consistent XHTML and OPF
declarations.
- Added CrossInk cache-clearing guidance to README.md.
- Worked around an epub-builder duplicate XML-ID defect discovered by
validation.

src/epub/templates/colophon.xhtml

@@ -7,17 +7,15 @@
         feed reader: entries are deduplicated, read in full, weighed against social
         proof, then scored, sectioned and introduced by a language model.
       </p>
-      <dl class="colophon-facts">
-        <dt class="fact-key">Issue</dt><dd class="fact-value">No. {{ issue_number }} &#183; {{ display_date }}</dd>
-        <dt class="fact-key">Generated</dt><dd class="fact-value">{{ generated_at }}</dd>
-        <dt class="fact-key">Curation model</dt><dd class="fact-value">{{ model }}</dd>
-        <dt class="fact-key">Entries considered</dt><dd class="fact-value">{{ entries_fetched }} from {{ feeds_seen }} feeds</dd>
-        <dt class="fact-key">Candidates scored</dt><dd class="fact-value">{{ candidates }}</dd>
-        <dt class="fact-key">Articles selected</dt><dd class="fact-value">{{ article_count }} across {{ section_count }} sections</dd>
-        <dt class="fact-key">Words</dt><dd class="fact-value">{{ total_words }} &#183; {{ reading_line }}</dd>
-        <dt class="fact-key">Token cost</dt><dd class="fact-value">{{ cost_usd }}</dd>
-        <dt class="fact-key">Generator</dt><dd class="fact-value">{{ generator_version }}</dd>
-      </dl>
+      <p class="fact-line"><strong>Issue:</strong> No. {{ issue_number }} &#183; {{ display_date }}</p>
+      <p class="fact-line"><strong>Generated:</strong> {{ generated_at }}</p>
+      <p class="fact-line"><strong>Curation model:</strong> {{ model }}</p>
+      <p class="fact-line"><strong>Entries considered:</strong> {{ entries_fetched }} from {{ feeds_seen }} feeds</p>
+      <p class="fact-line"><strong>Candidates scored:</strong> {{ candidates }}</p>
+      <p class="fact-line"><strong>Articles selected:</strong> {{ article_count }} across {{ section_count }} sections</p>
+      <p class="fact-line"><strong>Words:</strong> {{ total_words }} &#183; {{ reading_line }}</p>
+      <p class="fact-line"><strong>Token cost:</strong> {{ cost_usd }}</p>
+      <p class="fact-line"><strong>Generator:</strong> {{ generator_version }}</p>
       <p class="attribution">
         Article text belongs to its authors and publications; excerpts and links are
         provided for personal reading. Comment excerpts belong to their posters.

src/epub/templates/cover_page.xhtml

@@ -1,5 +1,5 @@
 {% extends "base.xhtml" %}
 {% block body_class %}cover-page{% endblock %}
 {% block content %}
-      <div class="cover-image"><img src="cover.png" alt="{{ alt }}"/></div>
+      <div class="cover-image"><img src="{{ cover_href }}" alt="{{ alt }}"/></div>
 {% endblock %}

src/epub/templates/style-x4.css

@@ -178,11 +178,15 @@ p.comment-line {
   margin: 0 0 0.35em 0;
 }
 
-dt.fact-key {
-  font-weight: bold;
-  margin-top: 0.35em;
+.world-summary {
+  margin: 0.2em 0 0.45em 0;
+  font-style: italic;
 }
 
-dd.fact-value {
-  margin: 0 0 0 0.8em;
+.world-overview {
+  margin-bottom: 0.7em;
+}
+
+.fact-line {
+  margin: 0 0 0.35em 0;
 }

src/epub/templates/style.css

@@ -275,16 +275,20 @@ blockquote.comment blockquote.comment {
   margin-bottom: 0.25em;
 }
 
+.world-summary {
+  margin: 0.2em 0 0.45em 0;
+  font-style: italic;
+}
+
+.world-overview {
+  margin-bottom: 0.7em;
+}
+
 .attribution {
   font-size: 0.8em;
   font-style: italic;
 }
 
-.colophon-facts dt {
-  font-variant: small-caps;
-  margin-top: 0.4em;
-}
-
-.colophon-facts dd {
-  margin: 0 0 0 1em;
+.fact-line {
+  margin: 0 0 0.35em 0;
 }