fix: playground captain v2 scenarios (#13747)

# Pull Request Template

## Description

Playground now uses v2. It was only wired to use v1. Traces get `source:
playground` on langfuse when playground has been used.

## Type of change

- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide
instructions so we can reproduce. Please also list any relevant details
for your test configuration.

locally and specs
<img width="1806" height="1276" alt="image"
src="https://github.com/user-attachments/assets/41ef4eb3-52b1-4b8e-9a4f-e8510c90cb39"
/>


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [x] Any dependent changes have been merged and published in downstream
modules

enterprise/app/controllers/api/v1/accounts/captain/assistants_controller.rb

@@ -24,10 +24,16 @@ class Api::V1::Accounts::Captain::AssistantsController < Api::V1::Accounts::Base
   end
 
   def playground
-    response = Captain::Llm::AssistantChatService.new(assistant: @assistant).generate_response(
-      additional_message: params[:message_content],
-      message_history: message_history
-    )
+    response = if captain_v2_enabled?
+                 Captain::Assistant::AgentRunnerService.new(assistant: @assistant, source: 'playground').generate_response(
+                   message_history: playground_message_history
+                 )
+               else
+                 Captain::Llm::AssistantChatService.new(assistant: @assistant, source: 'playground').generate_response(
+                   additional_message: playground_params[:message_content],
+                   message_history: message_history
+                 )
+               end
 
     render json: response
   end
@@ -64,10 +70,31 @@ class Api::V1::Accounts::Captain::AssistantsController < Api::V1::Accounts::Base
   end
 
   def playground_params
-    params.require(:assistant).permit(:message_content, message_history: [:role, :content])
+    params.require(:assistant).permit(:message_content, message_history: [:role, :content, :agent_name])
   end
 
   def message_history
-    (playground_params[:message_history] || []).map { |message| { role: message[:role], content: message[:content] } }
+    (playground_params[:message_history] || []).map do |message|
+      {
+        role: message[:role],
+        content: message[:content],
+        agent_name: message[:agent_name]
+      }.compact
+    end
+  end
+
+  def playground_message_history
+    history = message_history
+    current_message = playground_params[:message_content]
+    return history if current_message.blank?
+
+    current_user_message = { role: 'user', content: current_message }
+    return history if history.last == current_user_message
+
+    history + [current_user_message]
+  end
+
+  def captain_v2_enabled?
+    @assistant.account.feature_enabled?('captain_integration_v2')
   end
 end