CmdStan guide lacks doc on columns of `diagnose` output

[jgabry]

This came up in cmdstanr issue #826 from @ksvanhorn:

It's worth noting the the columns in the output aren't documented anywhere that I can find. I can guess what some of them are, but what are "param idx" and "value"?

One other note: it seems that the diagnose operation failed with a return code of 1, but none of the information I was able to gather told me why the program failed. I'm guessing that maybe an exception got thrown while evaluating an extremely large gradient, but it would be useful for the program to say more instead of just returning an error code of 1.

If I go to the CmdStan doc for the diagnose method I see that @ksvanhorn is right and the columns of the output have no explanations (although some are self explanatory, others could be a bit confusing, like param_idx).

[mitzimorris]

noted.
"param idx" is unfortunate. as the bernoulli model only has a single parameter, that what you get.
an improvement to the diagnose method would sub in the parameter name for the idx.