Add VSCode language model tool source type definitions

This change adds TypeScript definitions for language model tools from different sources including VS Code extensions and MCP (Model Context Protocol) servers. The new types provide source attribution and metadata for language model tools, enabling better tool management and user transparency about tool origins.

Co-authored-by: bamurtaugh <25310137+bamurtaugh@users.noreply.github.com>

Author: Copilot

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

@@ -265,6 +265,43 @@ declare module 'vscode' {
 		export const onDidChangeChatRequestTools: Event<ChatRequest>;
 	}
 
+	export class LanguageModelToolExtensionSource {
+		/**
+		 * ID of the extension that published the tool.
+		 */
+		readonly id: string;
+
+		/**
+		 * Label of the extension that published the tool.
+		 */
+		readonly label: string;
+
+		private constructor(id: string, label: string);
+	}
+
+	export class LanguageModelToolMCPSource {
+		/**
+		 * Editor-configured label of the MCP server that published the tool.
+		 */
+		readonly label: string;
+
+		/**
+		 * Server-defined name of the MCP server.
+		 */
+		readonly name: string;
+
+		/**
+		 * Server-defined instructions for MCP tool use.
+		 */
+		readonly instructions?: string;
+
+		private constructor(label: string, name: string, instructions?: string);
+	}
+
+	export interface LanguageModelToolInformation {
+		source: LanguageModelToolExtensionSource | LanguageModelToolMCPSource | undefined;
+	}
+
 	// TODO@API fit this into the stream
 	export interface ChatUsedContext {
 		documents: ChatDocumentContext[];