Add alpha software warning to README

- Add prominent warning at top of README indicating this is alpha software
- Warn users about potential breaking changes and instability
- Advise against production use
- Include specific warnings about incomplete features and documentation

Author: openhands-agent

README.md

@@ -1,5 +1,16 @@
 # OpenHands Agent Server TypeScript Client
 
+> ⚠️ **ALPHA SOFTWARE WARNING** ⚠️
+> 
+> This TypeScript SDK is currently in **alpha** and is **not stable**. The API may change significantly between versions without notice. This software is intended for early testing and development purposes only.
+> 
+> - Breaking changes may occur in any release
+> - Features may be incomplete or contain bugs
+> - Documentation may be outdated or incomplete
+> - Not recommended for production use
+> 
+> Please use with caution and expect frequent updates.
+
 A TypeScript client library for the OpenHands Agent Server API that mirrors the structure and functionality of the Python SDK.
 
 ## Features