feat: widen the default sidebar to 320px

Also renames .ai-history-item-preview to .ai-history-item-subtext: the
span holds Claude's session title now, not a preview of the chat.

Author: abose

src/styles/Extn-AIChatPanel.less

@@ -587,12 +587,12 @@
         flex-shrink: 0;
     }
 
-    /* Last prompt of the session, revealed on hover: always-on it made a
-       50-entry list too dense to scan. It keeps its space in the row while
-       hidden, so fading it in shifts nothing. Empty when it would only
-       repeat the title, and the separator hangs off the text so nothing
-       is drawn for those rows. */
-    .ai-history-item-preview {
+    /* Claude's title for the session, revealed on hover: always-on it made
+       a 50-entry list too dense to scan. It keeps its space in the row while
+       hidden, so showing it shifts nothing. Empty when it would only repeat
+       the headline, and the separator hangs off the text so nothing is
+       drawn for those rows. */
+    .ai-history-item-subtext {
         font-size: @ai-text-meta;
         color: @project-panel-text-2;
         // No transition: a fade here reads as lag when you are running the
@@ -610,7 +610,7 @@
         }
     }
 
-    &:hover .ai-history-item-preview {
+    &:hover .ai-history-item-subtext {
         opacity: 0.75;
     }
 

src/styles/brackets_variables.less

@@ -48,7 +48,7 @@
 @inline-triangle-size: 9px;
 
 /* Main layout */
-@sidebar-width: 270px;  // user resizable, however
+@sidebar-width: 320px;  // user resizable, however
 @main-toolbar-width: 30px;
 
 /* Extension Manager */