Add "new session" to chat context menu (#198376)

From discussion

src/vs/workbench/contrib/chat/browser/actions/chatClearActions.ts

@@ -63,12 +63,15 @@ export function registerClearActions() {
 						primary: KeyMod.WinCtrl | KeyCode.KeyL
 					},
 					when: CONTEXT_IN_CHAT_SESSION
+				},
+				menu: {
+					id: MenuId.ChatContext,
+					group: 'z_clear'
 				}
 			});
 		}
 
 		run(accessor: ServicesAccessor, ...args: any[]) {
-			announceChatCleared(accessor);
 			const widgetService = accessor.get(IChatWidgetService);
 
 			const widget = widgetService.lastFocusedWidget;
@@ -76,6 +79,7 @@ export function registerClearActions() {
 				return;
 			}
 
+			announceChatCleared(accessor);
 			widget.clear();
 		}
 	});

src/vs/workbench/contrib/chat/browser/actions/chatCopyActions.ts

@@ -23,7 +23,8 @@ export function registerChatCopyActions() {
 				f1: false,
 				category: CHAT_CATEGORY,
 				menu: {
-					id: MenuId.ChatContext
+					id: MenuId.ChatContext,
+					group: 'copy',
 				}
 			});
 		}
@@ -56,7 +57,8 @@ export function registerChatCopyActions() {
 				f1: false,
 				category: CHAT_CATEGORY,
 				menu: {
-					id: MenuId.ChatContext
+					id: MenuId.ChatContext,
+					group: 'copy',
 				}
 			});
 		}