chat: virtualize message-to-json conversion
Bad `@t` text might crash and fully halt the json conversion, preventing any
data from being delivered to the frontend.
Fixes
(fall ((ot output+(ar dank) ~) a) ~)
::
++ lett
+ =, enjs:format
|= =letter
^- json
- =, enjs:format
+ =; result=(each json tang)
+ ?- -.result
+ %& p.result
+ %| (frond %text s+'[[json rendering error]]')
+ ==
+ %- mule
+ |.
?- -.letter
%text
(frond %text s+text.letter)
