feat(web): lead summary detail with takeaways

The product promise is "decide what's worth your time", but the detail page
buried Takeaways — the verdict that answers that — below the full Summary.
Reorder to Takeaways → Highlights → Summary so the attention-saving payload
leads (UX review A8). Data already existed; this is a section reorder only.
Conditional sections mean a video without takeaways/highlights still leads
with the Summary naturally.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/web/handlers_test.go

@@ -234,6 +234,14 @@ func TestDetailRendersHighlightsAndTakeaways(t *testing.T) {
 	require.Contains(t, html, "takeaway one")
 	require.Contains(t, html, `id="action-buttons"`, "action button group present")
 	require.Contains(t, html, "Watched")
+
+	// The detail page leads with the attention-saving payload (UX review A8):
+	// Takeaways ("is it worth my time?") above Highlights above the full Summary.
+	takeaways := strings.Index(html, "takeaway one")
+	highlights := strings.Index(html, "highlight one")
+	summary := strings.Index(html, "the full summary body")
+	require.Less(t, takeaways, highlights, "Takeaways render before Highlights")
+	require.Less(t, highlights, summary, "Highlights render before the full Summary")
 }
 
 func TestDetailNotFound(t *testing.T) {