fix(ui): suppress double scrollbar in log + timeline panels

LogViewer and EventFeed each apply overflow-y:auto to their root
container, which produced a nested scrollbar inside the
InfiniteScrollArea that also scrolls. A flatScroll override class
flattens the DS component so the outer InfiniteScrollArea owns the
single scrollbar — matching the IntersectionObserver sentinels that
drive infinite-load.

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

ui/src/pages/AgentHealth/AgentHealth.tsx

@@ -966,7 +966,7 @@ export default function AgentHealth() {
             maxHeight={360}
           >
             {filteredLogs.length > 0 ? (
-              <LogViewer entries={filteredLogs} />
+              <LogViewer entries={filteredLogs} className={logStyles.flatScroll} />
             ) : (
               <div className={logStyles.logEmpty}>
                 {logSearch || logLevels.size > 0 || logSources.size > 0
@@ -1004,7 +1004,7 @@ export default function AgentHealth() {
             maxHeight={360}
           >
             {feedEvents.length > 0 ? (
-              <EventFeed events={feedEvents} />
+              <EventFeed events={feedEvents} className={logStyles.flatScroll} />
             ) : (
               <div className={logStyles.logEmpty}>
                 {eventStream.isLoading ? 'Loading events\u2026' : 'No events in the selected time range.'}

ui/src/pages/AgentInstance/AgentInstance.tsx

@@ -472,7 +472,7 @@ export default function AgentInstance() {
             maxHeight={360}
           >
             {filteredLogs.length > 0 ? (
-              <LogViewer entries={filteredLogs} />
+              <LogViewer entries={filteredLogs} className={logStyles.flatScroll} />
             ) : (
               <div className={logStyles.logEmpty}>
                 {logSearch || logLevels.size > 0 || logSources.size > 0
@@ -510,7 +510,7 @@ export default function AgentInstance() {
             maxHeight={360}
           >
             {feedEvents.length > 0 ? (
-              <EventFeed events={feedEvents} />
+              <EventFeed events={feedEvents} className={logStyles.flatScroll} />
             ) : (
               <div className={logStyles.logEmpty}>
                 {eventStream.isLoading ? 'Loading events…' : 'No events in the selected time range.'}

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

@@ -9,6 +9,16 @@
   max-height: 420px;
 }
 
+/*
+ * Flatten the internal scroll of @cameleer/design-system's LogViewer and
+ * EventFeed so their containing InfiniteScrollArea owns the scroll — one
+ * scrollbar per panel, IntersectionObserver sentinels stay meaningful.
+ */
+.flatScroll {
+  overflow: visible !important;
+  max-height: none !important;
+}
+
 .logHeader {
   display: flex;
   align-items: center;