Fix session sidebar scrollbar - make it visible and functional

- Add CSS for .chat-history-list (was missing, only had .chat-sessions-list)
- Add custom scrollbar styling for better UX
- Add min-height: 0 to fix flexbox overflow issue
- Update cache buster (v1769092045) to force CSS reload

Fixes issue where long session lists had no scrollbar, making bottom
sessions inaccessible.

Co-Authored-By: Claude <noreply@anthropic.com>

public/claude-ide/ide.css

@@ -592,10 +592,30 @@ body {
   flex-direction: column;
 }
 
-.chat-sessions-list {
+.chat-sessions-list,
+.chat-history-list {
   flex: 1;
   overflow-y: auto;
   padding: 1rem;
+  min-height: 0;
+}
+
+/* Custom scrollbar for chat history list */
+.chat-history-list::-webkit-scrollbar {
+  width: 8px;
+}
+
+.chat-history-list::-webkit-scrollbar-track {
+  background: var(--bg-secondary);
+}
+
+.chat-history-list::-webkit-scrollbar-thumb {
+  background: var(--border);
+  border-radius: 4px;
+}
+
+.chat-history-list::-webkit-scrollbar-thumb:hover {
+  background: var(--text-secondary);
 }
 
 .chat-main {
@@ -1764,6 +1784,7 @@ body {
 
 /* Hide scrollbar but keep functionality */
 @media (max-width: 768px) {
+    /* Hide scrollbars on mobile for cleaner UI */
     .chat-messages::-webkit-scrollbar,
     .chat-history-list::-webkit-scrollbar,
     .sessions-list::-webkit-scrollbar {