Fix toggle click and directory stat display bugs in ChatView

- Fix first toggle click failing for unregistered top-level directories by
  passing the effective expanded state to toggleDirectory instead of toggling
  the raw (possibly undefined) state value.
- Fix directory nodes showing +0/-0 when all children lack stats by guarding
  DiffStatLabel render with hasNonZeroStat, consistent with file nodes and
  the summary header.

Co-authored-by: Julius Marminge <juliusmarminge@users.noreply.github.com>

Author: cursoragent

apps/web/src/components/ChatView.tsx

@@ -3176,10 +3176,10 @@ const ChangedFilesTree = memo(function ChangedFilesTree(props: {
     () => buildInitiallyExpandedDirectoryState(treeNodes),
   );
 
-  const toggleDirectory = useCallback((pathValue: string) => {
+  const toggleDirectory = useCallback((pathValue: string, currentlyExpanded: boolean) => {
     setExpandedDirectories((current) => ({
       ...current,
-      [pathValue]: !current[pathValue],
+      [pathValue]: !currentlyExpanded,
     }));
   }, []);
 
@@ -3193,7 +3193,7 @@ const ChangedFilesTree = memo(function ChangedFilesTree(props: {
             type="button"
             className="group flex w-full items-center gap-1.5 rounded-md py-1 pr-2 text-left hover:bg-background/80"
             style={{ paddingLeft: `${leftPadding}px` }}
-            onClick={() => toggleDirectory(node.path)}
+            onClick={() => toggleDirectory(node.path, isExpanded)}
           >
             <ChevronRightIcon
               aria-hidden="true"
@@ -3210,9 +3210,11 @@ const ChangedFilesTree = memo(function ChangedFilesTree(props: {
             <span className="truncate font-mono text-[11px] text-muted-foreground/90 group-hover:text-foreground/90">
               {node.name}
             </span>
-            <span className="ml-auto shrink-0 font-mono text-[10px] tabular-nums">
-              <DiffStatLabel additions={node.stat.additions} deletions={node.stat.deletions} />
-            </span>
+            {hasNonZeroStat(node.stat) && (
+              <span className="ml-auto shrink-0 font-mono text-[10px] tabular-nums">
+                <DiffStatLabel additions={node.stat.additions} deletions={node.stat.deletions} />
+              </span>
+            )}
           </button>
           {isExpanded && (
             <div className="space-y-0.5">