dashboard: add 'Event Log' subtitle above filtered table on progress page

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

dashboard/src/progress.md

@@ -79,6 +79,8 @@ display(byDay.length === 0
 );
 ```
 
+## Event Log
+
 ```js
 const authorOpts = ["(all)", ...new Set(data.map(e => e.author ?? "unknown"))].sort();
 const typeOpts   = ["(all)", ...new Set(data.map(e => e.event_type))].sort();