`kore-rpc` returns error response on request with Unicode character

For a request that contains Unicode characters within a string (either escaped or not), kore-rpc returns error -32602 Invalid params.

Steps to reproduce

string-rewrite.k
request.json

$ kompile string-rewrite.k --backend haskell
$ kore-rpc string-rewrite-kompiled/definition.kore --module STRING-REWRITE --server-port 3000

$ netcat -q 0 localhost 3000 < request.json
{"jsonrpc":"2.0","id":1,"error":{"code":-32602,"data":{"state":{"format":"KORE","version":1,"term":{"tag":"App","name":"Lbl'-LT-'generatedTop'-GT-'","sorts":[],"args":[{"tag":"App","name":"Lbl'-LT-'k'-GT-'","sorts":[],"args":[{"tag":"App","name":"kseq","sorts":[],"args":[{"tag":"App","name":"inj","sorts":[{"tag":"SortApp","name":"SortString","args":[]},{"tag":"SortApp","name":"SortKItem","args":[]}],"args":[{"tag":"DV","sort":{"tag":"SortApp","name":"SortString","args":[]},"value":"🙂"}]},{"tag":"App","name":"dotk","sorts":[],"args":[]}]}]},{"tag":"App","name":"Lbl'-LT-'generatedCounter'-GT-'","sorts":[],"args":[{"tag":"DV","sort":{"tag":"SortApp","name":"SortInt","args":[]},"value":"0"}]},{"tag":"App","name":"Lbl'-LT-'s'-GT-'","sorts":[],"args":[{"tag":"DV","sort":{"tag":"SortApp","name":"SortString","args":[]},"value":""}]}]}}},"message":"Invalid params"}}

The error is due to

{
  "tag": "DV",
  "sort": {
    "tag": "SortApp",
    "name": "SortString",
    "args": []
  },
  "value": "\ud83d\ude42"
}

on lines 40-47 of request.json. If the value is changed to

"value": "🙂"

the error is still there. Note that both strings are well-formed JSON strings (standard, see section 2.5).

If the value it's changed to

"value": "hello"

the request works as expected:

{"jsonrpc":"2.0","id":1,"result":{"reason":"stuck","depth":1,"state":{"term":{"format":"KORE","version":1,"term":{"tag":"App","name":"Lbl'-LT-'generatedTop'-GT-'","sorts":[],"args":[{"tag":"App","name":"Lbl'-LT-'k'-GT-'","sorts":[],"args":[{"tag":"App","name":"dotk","sorts":[],"args":[]}]},{"tag":"App","name":"Lbl'-LT-'generatedCounter'-GT-'","sorts":[],"args":[{"tag":"DV","sort":{"tag":"SortApp","name":"SortInt","args":[]},"value":"0"}]},{"tag":"App","name":"Lbl'-LT-'s'-GT-'","sorts":[],"args":[{"tag":"DV","sort":{"tag":"SortApp","name":"SortString","args":[]},"value":"hello"}]}]}}}}}

Reproduce the failure with string-rewrite.k, request.json, kompile, and the kore-rpc entry point. Trace how kore-rpc handles the SortString DV value for both escaped and literal Unicode, then verify that both request forms succeed while the existing ASCII case remains working.