fix(cli): surface agent_custom_instructions on add in both CLIs (#6910)

cli/node/src/backend/base.ts

@@ -15,6 +15,7 @@ export interface AddOptions {
 	infer?: boolean;
 	expires?: string;
 	customInstructions?: string;
+	agentCustomInstructions?: string;
 	customCategories?: Record<string, string>[];
 	structuredDataSchema?: Record<string, unknown>;
 	timestamp?: number;

cli/node/src/backend/platform.ts

@@ -153,6 +153,8 @@ export class PlatformBackend implements Backend {
 		if (opts.expires) payload.expiration_date = opts.expires;
 		if (opts.customInstructions)
 			payload.custom_instructions = opts.customInstructions;
+		if (opts.agentCustomInstructions)
+			payload.agent_custom_instructions = opts.agentCustomInstructions;
 		if (opts.customCategories)
 			payload.custom_categories = opts.customCategories;
 		if (opts.structuredDataSchema)