fix(ui): cascade flatScroll override to descendants

EventFeed's overflow-y:auto lives on its inner .list, not the root
where className lands. Extending .flatScroll to .flatScroll * covers
nested scroll containers, and relaxing the root's height:100% (which
EventFeed sets) lets content size naturally so the outer
InfiniteScrollArea owns the single scrollbar.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/src/styles/log-panel.module.css

@@ -14,11 +14,20 @@
  * EventFeed so their containing InfiniteScrollArea owns the scroll — one
  * scrollbar per panel, IntersectionObserver sentinels stay meaningful.
  */
-.flatScroll {
+.flatScroll,
+.flatScroll * {
   overflow: visible !important;
   max-height: none !important;
 }
 
+/* EventFeed root is flex column with height:100% and its .list child has
+   flex:1 + overflow-y:auto. Breaking the height chain lets content size
+   to itself so the InfiniteScrollArea wrapper scrolls once. */
+.flatScroll {
+  height: auto !important;
+  min-height: 0 !important;
+}
+
 .logHeader {
   display: flex;
   align-items: center;