Require JSON output for tools

[charleslien]

No description provided.

[charleslien]

What needs to be done:

1. Review the changes made in the "require json output for tool results" commit:

• Namely, changed ToolResultOutput from (json | media) to {value: json, media?: media[]}

2. Change all instances of ToolResultOutput[] to ToolResultOutput
3. Fix all the resulting type errors

[charleslien]

Note: perhaps the changing instances of ToolResultOutput[] to ToolResultOutput would be easier if you renamed the new one something different (like ToolResultContent)? then the typechecker would tell you where all the instances of ToolResultOutput are, since that variable no longer exists