Complete implementation: code review and security checks passed

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

Author: Copilot

src/@types/vscode.proposed.chatSessionsProvider.d.ts

@@ -95,6 +95,11 @@ declare module 'vscode' {
 		 */
 		description?: string | MarkdownString;
 
+		/**
+		 * An optional badge that provides additional context about the chat session.
+		 */
+		badge?: string | MarkdownString;
+
 		/**
 		 * An optional status indicating the current state of the session.
 		 */