Bot sends Adaptive Card but renders blank, partial, shows "Error encountered while rendering this message", or actions fail in Teams clients (desktop/web/mobile).

Teams clients have incomplete support for newer Adaptive Cards schema versions (>1.4 general, >1.2 mobile), causing parsing/rendering failures. v1.5+ features are unsupported post-client updates ([Teams Q&A 2025](https://learn.microsoft.com/en-us/answers/questions/5570683)).