Add official unsandbox.com JavaScript SDK

- Add lib/un.js (official async SDK from unsandbox.com)
- Add update-unsandbox-sdk Makefile target for SDK updates
- Note: SDK is Node.js-based, browser code-execution.js remains separate

Makefile

@@ -4,6 +4,7 @@
 # All phony targets
 .PHONY: help format check test validate-exports validate-all clean install dev build deploy
 .PHONY: languages-list languages-build-all languages-test-all languages-clean
+.PHONY: update-unsandbox-sdk
 
 # Environment variables for testing language implementations
 MODEL_ENDPOINT_1 ?= https://hermes.ai.unturf.com/v1
@@ -33,6 +34,7 @@ help:
 	@echo "  make git-add          - Stage all changes"
 	@echo "  make git-commit       - Commit with biome formatting"
 	@echo "  make git-push         - Push to remote"
+	@echo "  make update-unsandbox-sdk - Download latest un.js SDK from unsandbox.com"
 	@echo ""
 	@echo "Language Examples:"
 	@echo "  make languages-list           - List all language directories"
@@ -126,6 +128,13 @@ clean:
 	find . -name "*.log" -delete
 	find . -name "node_modules" -type d -exec rm -rf {} +
 
+# Download latest unsandbox.com JavaScript SDK (Node.js)
+update-unsandbox-sdk:
+	@echo "Downloading latest un.js SDK..."
+	@mkdir -p lib
+	wget -O lib/un.js "https://git.unturf.com/engineering/unturf/un-inception/-/raw/main/clients/javascript/async/src/un_async.js"
+	@echo "Done. Updated lib/un.js (Node.js SDK)"
+
 # Language validation
 validate-languages:
 	@echo "Validating language files..."