[FR]: Support unicode yaml formatting in span i/o view

Proposal summary

It looks like the span input/output view doesn’t really “format” unicode character containing YAML strings as you might expect. I "falls back" to a single string i.e. without yaml indentations and newlines. I think the formatter just needs to support unicode to make it all work.

Motivation

I inspect other spans other than the llm calls that have "pretty" mode. Unformatted yaml is hard to read and I need unicode for my activities.

For instance, when you have a span for a prompt formatter, you’ll notice two things happening:

Input ex. for a single span:

Argument	Value Example	Notes
arg1	<normal_yaml_str>	This part renders properly
arg2	<unicode_yaml_str>	This part is just one long string, with \n shown literally

Resulting output ex.: Since the prompt is just one long string including sections of yaml strings, the whole prompt isn’t rendered correctly - \n shows up as text instead of making new lines.

However, if you avoid using unicode, currently YAML mode formats things nicely and shows the yaml indentations and newlines as expected in all cases.