docs(readme): add multilingual announcement board and oauth warning

README.md

@@ -46,6 +46,15 @@ Built by students and members of the Harvard, MIT, and Sundai.Club communities.
 
 <p align="center"><code>Trait-driven architecture · secure-by-default runtime · provider/channel/tool swappable · pluggable everything</code></p>
 
+### 📢 Announcements
+
+Use this board for important notices (breaking changes, security advisories, maintenance windows, and release blockers).
+
+| Date (UTC) | Level | Notice | Action |
+|---|---|---|---|
+| 2026-02-19 | _Important_ | We have **not** launched an official website yet, and we are seeing impersonation attempts. Do **not** join any investment or fundraising activity claiming the ZeroClaw name. | Use this repository as the single source of truth. Follow [X (@zeroclawlabs)](https://x.com/zeroclawlabs?s=21) and [Xiaohongshu](https://www.xiaohongshu.com/user/profile/67cbfc43000000000d008307?xsec_token=AB73VnYnGNx5y36EtnnZfGmAmS-6Wzv8WMuGpfwfkg6Yc%3D&xsec_source=pc_search) for official updates. |
+| 2026-02-19 | _Important_ | Anthropic updated the Authentication and Credential Use terms on 2026-02-19. OAuth authentication (Free, Pro, Max) is intended exclusively for Claude Code and Claude.ai; using OAuth tokens from Claude Free/Pro/Max in any other product, tool, or service (including Agent SDK) is not permitted and may violate the Consumer Terms of Service. | Please temporarily avoid Claude Code OAuth integrations to prevent potential loss. Original clause: [Authentication and Credential Use](https://code.claude.com/docs/en/legal-and-compliance#authentication-and-credential-use). |
+
 ### ✨ Features
 
 - 🏎️ **Lean Runtime by Default:** Common CLI and status workflows run in a few-megabyte memory envelope on release builds.