fix: anchor saved scroll position by timestamp instead of index

Store the first visible entry's timestamp (stable across buffer
eviction) rather than its array index. On restore, resolve the
timestamp back to the current index via findEntryIndexByTime so
the scroll position survives head eviction while minimized.

Author: joshuapare

ui/providers/BottomDrawer/containers/LogViewer/index.tsx

@@ -163,10 +163,13 @@ const LogViewerContainer: React.FC<Props> = ({ sessionId, source, toolbarPrefix,
   followRef.current = follow;
   const filteredLineCountRef = useRef(filteredLineCount);
   filteredLineCountRef.current = filteredLineCount;
+  const filteredEntriesRef = useRef(filteredEntries);
+  filteredEntriesRef.current = filteredEntries;
 
   // Re-pin to bottom (or restore position) when the scroll container resizes.
   // This covers drawer drag-resize, minimize/re-expand, and fullscreen toggle.
-  const savedFirstVisibleRef = useRef<number | null>(null);
+  // We store a timestamp (not an index) so the anchor survives buffer eviction.
+  const savedVisibleTimestampRef = useRef<string | null>(null);
   const lastContainerHeightRef = useRef(0);
 
   React.useEffect(() => {
@@ -188,24 +191,33 @@ const LogViewerContainer: React.FC<Props> = ({ sessionId, source, toolbarPrefix,
               isAutoScrolling.current = false;
             });
           });
-        } else if (prevHeight === 0 && savedFirstVisibleRef.current !== null) {
-          // Restoring from minimized without follow: jump back to saved position
-          isAutoScrolling.current = true;
-          rowVirtualizer.scrollToIndex(savedFirstVisibleRef.current, { align: 'start' });
-          savedFirstVisibleRef.current = null;
-          requestAnimationFrame(() => {
+        } else if (prevHeight === 0 && savedVisibleTimestampRef.current !== null) {
+          // Restoring from minimized without follow: resolve saved timestamp to current index
+          const idx = findEntryIndexByTime(
+            filteredEntriesRef.current,
+            new Date(savedVisibleTimestampRef.current),
+          );
+          savedVisibleTimestampRef.current = null;
+          if (idx >= 0) {
+            isAutoScrolling.current = true;
+            rowVirtualizer.scrollToIndex(idx, { align: 'start' });
             requestAnimationFrame(() => {
-              isAutoScrolling.current = false;
+              requestAnimationFrame(() => {
+                isAutoScrolling.current = false;
+              });
             });
-          });
+          }
         }
       }
 
-      // Save the first visible index before the container collapses
+      // Save the first visible entry's timestamp before the container collapses
       if (prevHeight > 0 && newHeight === 0 && !followRef.current) {
         const range = rowVirtualizer.range;
         if (range) {
-          savedFirstVisibleRef.current = range.startIndex;
+          const entry = filteredEntriesRef.current[range.startIndex];
+          if (entry?.timestamp) {
+            savedVisibleTimestampRef.current = entry.timestamp;
+          }
         }
       }