Fix: skip unresolvable example links during export

The book contains org-mode link examples (e.g. [[*Project Alpha]],
[[id:meeting-2025-01-15]]) that are for illustration only and don't
resolve to real targets. Set org-export-with-broken-links t so the
exporter skips them gracefully instead of crashing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: DavidLiedle

publish.el

@@ -21,7 +21,10 @@
       ;; not a notebook. Blocks are displayed verbatim.
       org-export-use-babel nil
       ;; Convert file:chapter.org links → chapter.html in HTML export
-      org-html-link-org-files-as-html t)
+      org-html-link-org-files-as-html t
+      ;; Example links in the text (e.g. [[*Project Alpha]]) won't
+      ;; resolve — skip them rather than crashing.
+      org-export-with-broken-links t)
 
 ;; Use htmlize for syntax highlighting when available
 (when (require 'htmlize nil t)