fix(agent): resolve issue with custom fields in message

- Update request handling for custom fields
- Replace generic content formatting with actual prompt text

Author: phodal

core/src/main/kotlin/cc/unitmesh/devti/agent/custom/CustomAgentExecutor.kt

@@ -34,12 +34,18 @@ class CustomAgentExecutor(val project: Project) : CustomSSEProcessor(project) {
         this.responseFormat = agent.connector?.responseFormat ?: this.responseFormat
 
         val customRequest = CustomRequest(listOf(Message("user", promptText)))
-        val request = if (requestFormat.isNotEmpty()) {
+        var request = if (requestFormat.isNotEmpty()) {
             customRequest.updateCustomFormat(requestFormat)
         } else {
             Json.encodeToString<CustomRequest>(customRequest)
         }
 
+        // fix for custom fields in message replace \"content\": \"$content\" with \"$content\": promptText
+        val errorContent = "\"content\":\"\$content\""
+        if (request.contains(errorContent)) {
+            request = request.replace(errorContent, "\"content\": \"$promptText\"")
+        }
+
         val body = request.toRequestBody("application/json".toMediaTypeOrNull())
         val builder = Request.Builder()