Clear partial query quick chats when closed

Fixes microsoft/vscode-copilot#2353

src/vs/workbench/contrib/chat/browser/chatQuick.ts

@@ -7,7 +7,7 @@ import * as dom from 'vs/base/browser/dom';
 import { Orientation, Sash } from 'vs/base/browser/ui/sash/sash';
 import { disposableTimeout } from 'vs/base/common/async';
 import { CancellationToken } from 'vs/base/common/cancellation';
-import { Emitter } from 'vs/base/common/event';
+import { Emitter, Event } from 'vs/base/common/event';
 import { Disposable, DisposableStore, IDisposable, MutableDisposable } from 'vs/base/common/lifecycle';
 import { Selection } from 'vs/editor/common/core/selection';
 import { IContextKeyService } from 'vs/platform/contextkey/common/contextkey';
@@ -61,6 +61,14 @@ export class QuickChatService extends Disposable implements IQuickChatService {
 			this.close();
 		} else {
 			this.open(providerId, options);
+			// If this is a partial query, the value should be cleared when closed as otherwise it
+			// would remain for the next time the quick chat is opened in any context.
+			if (options?.isPartialQuery) {
+				const disposable = this._store.add(Event.once(this.onDidClose)(() => {
+					this._currentChat?.clearValue();
+					this._store.delete(disposable);
+				}));
+			}
 		}
 	}
 
@@ -300,6 +308,10 @@ class QuickChat extends Disposable {
 		this.focus(selection);
 	}
 
+	clearValue(): void {
+		this.widget.inputEditor.setValue('');
+	}
+
 	private updateModel(): void {
 		this.model ??= this.chatService.startSession(this._options.providerId, CancellationToken.None);
 		if (!this.model) {