Msg Shard should only take String rvalues and is not intended for variables, including argument values

[Yttruire]

Describe the bug

The Msg shard currently displays the values of variables, and parameters. By design, this is not intentional, and should only print String messages that have been input directly as-is. Use Log for printing variable values to console. The error message output should also be updated accordingly to be more specific than a type mismatch (See #673).

To Reproduce

The following code example is from the current (12/5/23) Shards documentation. This code runs and prints the values of the arguments. This is not intentional by design.

(defshards msgshard [a b]
  (Msg a)  ;; print value of 1st arg passed
  (Msg b)) ;; print value of 2nd arg passed

(Msg "Hello World") ;; prints string
(msgshard "Bye" "Universe") ;; prints args passed

Expected behavior

An error should occur.