fix: cap day-highlights chips at 50; show J/K hint when over limit

Rendering 793 individual buttons is both visually overwhelming and slow.
When a day has more than 50 loud sections, replace the chip list with a
single note ("N sections — use J / K to navigate"). J/K navigation and
the SVG timeline still cover all sections.

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

web.py

@@ -1472,6 +1472,14 @@ async function dayHighlights(dayId, analyzableFiles) {
   box.appendChild(labels);
 
   if (dayActiveSections.length) {
+    const MAX_DAY_CHIPS = 50;
+    if (dayActiveSections.length > MAX_DAY_CHIPS) {
+      const note = document.createElement('p');
+      note.className = 'quiet';
+      note.style.marginTop = '6px';
+      note.textContent = `${dayActiveSections.length} sections — use J / K to navigate`;
+      box.appendChild(note);
+    } else {
       const chips = document.createElement('div');
       chips.className = 'chips';
       chips.setAttribute('role', 'list');
@@ -1491,6 +1499,7 @@ async function dayHighlights(dayId, analyzableFiles) {
       });
       box.appendChild(chips);
     }
+  }
 
   const summary = document.createElement('div');
   summary.className = 'quiet';