feat: v1.2.5 — UI improvements and session management fixes

- Fix session delete to scan all claude project dirs (not just first match)
- Batch async rendering for message history with stale render guard
- Add custom draggable scrollbar for chat area
- Fix AskUserQuestion card rendered at bottom instead of top
- Fix bubble split (msg-text + msg-tools) to prevent tool UI overwrite
- Add delete confirmation dialog with warm theme styling
- Support multiline display in user messages
- Apply model config to settings.json immediately on save

public/index.html

@@ -56,11 +56,16 @@
         <span id="cost-display" class="cost-display"></span>
       </header>
 
-      <div id="messages" class="messages">
-        <div class="welcome-msg">
-          <div class="welcome-icon">✿</div>
-          <h3>欢迎使用 CC-Web</h3>
-          <p>开始与 Claude Code 对话</p>
+      <div class="messages-wrap">
+        <div id="messages" class="messages">
+          <div class="welcome-msg">
+            <div class="welcome-icon">✿</div>
+            <h3>欢迎使用 CC-Web</h3>
+            <p>开始与 Claude Code 对话</p>
+          </div>
+        </div>
+        <div class="custom-scrollbar" id="custom-scrollbar">
+          <div class="custom-scrollbar-thumb" id="custom-scrollbar-thumb"></div>
         </div>
       </div>