feat: include fields in prompt only when there are fields

This essentially allows tools to "display" info to a user, even when
using SDKs.

Signed-off-by: Donnie Adams <[email protected]>

Author: thedadams

pkg/prompt/prompt.go

@@ -61,9 +61,13 @@ func SysPrompt(ctx context.Context, envs []string, input string, _ chan<- string
 
 	for _, env := range envs {
 		if url, ok := strings.CutPrefix(env, types.PromptURLEnvVar+"="); ok {
+			var fields []string
+			if params.Fields != "" {
+				fields = strings.Split(params.Fields, ",")
+			}
 			httpPrompt := types.Prompt{
 				Message:   params.Message,
-				Fields:    strings.Split(params.Fields, ","),
+				Fields:    fields,
 				Sensitive: params.Sensitive == "true",
 			}
 			return sysPromptHTTP(ctx, envs, url, httpPrompt)