chat: refactor model picker delegate and improve picker UX

src/vs/platform/actionWidget/browser/actionList.ts

@@ -810,7 +810,7 @@ export class ActionList<T> extends Disposable {
 			availableHeight = widgetTop > 0 ? windowHeight - widgetTop - padding : windowHeight * 0.7;
 		}
 
-		const viewportMaxHeight = Math.floor(targetWindow.innerHeight * 0.4);
+		const viewportMaxHeight = Math.floor(targetWindow.innerHeight * 0.6);
 		const maxHeight = Math.min(Math.max(availableHeight, this._actionLineHeight * 3 + filterHeight), viewportMaxHeight);
 		const height = Math.min(listHeight + filterHeight, maxHeight);
 		return height - filterHeight;

src/vs/sessions/contrib/chat/browser/newChatViewPane.ts

@@ -686,7 +686,8 @@ class NewChatWidget extends Disposable implements IHistoryNavigationWidget {
 				this._focusEditor();
 			},
 			getModels: () => this._getAvailableModels(),
-			canManageModels: () => true,
+			useGroupedModelPicker: () => true,
+			showManageModelsAction: () => false,
 		};
 
 		const pickerOptions: IChatInputPickerOptions = {

src/vs/workbench/contrib/chat/browser/widget/input/chatInputPart.ts

@@ -2225,7 +2225,8 @@ export class ChatInputPart extends Disposable implements IHistoryNavigationWidge
 							this.renderAttachedContext();
 						},
 						getModels: () => this.getModels(),
-						canManageModels: () => {
+						useGroupedModelPicker: () => true,
+						showManageModelsAction: () => {
 							const sessionType = this.getCurrentSessionType();
 							return !sessionType || sessionType === localChatSessionType;
 						}