toc fix: urls can't be embedded under files

Author: jeremymanning

content/_toc.yml

@@ -26,10 +26,8 @@ parts:
       - file: themes/final_projects/placeholder.md
   - caption: Slides
     chapters:
-    - file: slides/links
-      sections:
-        - url: slides/welcome.html
-          title: Welcome and overview
+    - url: slides/welcome.html
+      title: Welcome and overview
   - caption: Assignments
     chapters:
     - file: assignments/README

content/slides/links.md

@@ -1,3 +1,4 @@
 # Downloadable slides
 
-- April 3, 2025: [Welcome and overview](welcome.html)
+### April 3, 2025:
+  - [Welcome and overview](welcome.html)