feat(ai): split AI panel header actions into left and right groups

Mirrors the existing right-actions absolute layout on the left so session
ops (new, history) live on the left edge of the header while Settings
stays on the far right. Both groups share the hover-to-reveal behavior.

Author: abose

src/styles/Extn-AIChatPanel.less

@@ -77,9 +77,9 @@
         line-height: 19px;
     }
 
-    .ai-chat-header-actions {
+    .ai-chat-header-actions,
+    .ai-chat-header-left-actions {
         position: absolute;
-        right: 10px;
         display: flex;
         align-items: center;
         gap: 2px;
@@ -88,6 +88,14 @@
         transition: opacity 0.5s ease;
     }
 
+    .ai-chat-header-actions {
+        right: 10px;
+    }
+
+    .ai-chat-header-left-actions {
+        left: 10px;
+    }
+
     .ai-history-btn,
     .ai-settings-btn {
         display: flex;
@@ -113,7 +121,8 @@
 }
 
 /* Show header actions on tab container hover */
-.ai-tab-container:hover .ai-chat-header-actions {
+.ai-tab-container:hover .ai-chat-header-actions,
+.ai-tab-container:hover .ai-chat-header-left-actions {
     opacity: 1;
     pointer-events: auto;
     transition: opacity 0.15s ease;