Sync chatSessionCustomizationProvider d.ts with VS Code origin/main

Add groupKey, badge, and badgeTooltip fields to ChatSessionCustomizationItem
to match upstream changes from #305810 and #305813.

The providers don't set these fields explicitly — the VS Code UI
auto-enriches instruction items by parsing frontmatter when groupKey
is not provided.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: joshspicer

src/extension/vscode.proposed.chatSessionCustomizationProvider.d.ts

@@ -41,7 +41,8 @@ declare module 'vscode' {
 
 	/**
 	 * Metadata describing a customization provider and its capabilities.
-	 * This drives UI presentation (label, icon) and filtering (unsupported types).
+	 * This drives UI presentation (label, icon) and filtering (unsupported types,
+	 * workspace sub-paths).
 	 */
 	export interface ChatSessionCustomizationProviderMetadata {
 		/**
@@ -85,6 +86,27 @@ declare module 'vscode' {
 		 * Optional description of this customization.
 		 */
 		readonly description?: string;
+
+		/**
+		 * Optional group key for display grouping. Items sharing the same
+		 * `groupKey` are placed under a shared collapsible header in the
+		 * management UI.
+		 *
+		 * When omitted, items are grouped automatically by their storage
+		 * source (e.g. Workspace, User) based on the item's URI.
+		 */
+		readonly groupKey?: string;
+
+		/**
+		 * Optional inline badge text shown next to the item name
+		 * (e.g. a glob pattern like `src/vs/sessions/**`).
+		 */
+		readonly badge?: string;
+
+		/**
+		 * Optional tooltip text shown when hovering over the badge.
+		 */
+		readonly badgeTooltip?: string;
 	}
 
 	/**