basic-host does not forward toolResult _meta to the ui.

[zekebergida]

Describe the bug
in basic-host tool-result meta does not get sent to the ui. only content and structuredContent are sent.

To Reproduce
Steps to reproduce the behavior:

1. add _meta object to tool result. try to access it from the ui along side content and structuredContent

Expected behavior
toolResult _meta should be available to the ui as documented here

Logs
If applicable, add logs to help explain your problem.

Additional context
Open ai is having this problem as well. Claude does send the _meta to the ui and it can be read by apps.