Not yet .. but we have a design for tracing the execution flow of every run at near zero cost and then playing back the execution trace. That's not saving all intermediate state but if you save the input (usually an HTTP request; so its saved in the logs) then you can easily debug production issues with it.

If you meant debugging type stuff yes there's debugging already, including from the Idea plugin.

Could one eventually build a TCP in Ballerina where the animated diagram is the program?

I missed replying to this .. yes one could easily.

Making that perform at the same level as a TCP driver written in C could be a bit challenging .. but not impossible.

In fact, expressing network interaction protocols is one motivation for the sequence diagram approach, but the expectation was higher level stuff like OpenID or SAML type interactions.