fix(captain): display handoff message to customer in V2 flow (#13885)

HandoffTool changes conversation status but only posts a private note.
ResponseBuilderJob now detects the tool flag and creates the public
handoff message that was previously only shown in V1.

# Pull Request Template

## Description

Captain V2 was silently forwarding conversations to humans without
showing a handoff message to the customer. The conversation appeared to
just stop
responding.

Root cause: In V2, HandoffTool calls bot_handoff! during agent
execution, which changes conversation status from pending to open. By
the time control returns
to ResponseBuilderJob#process_response, the conversation_pending? guard
returns early - skipping create_handoff_message entirely. The V1 flow
didn't have this
problem because AssistantChatService just returns a string token
(conversation_handoff) and lets ResponseBuilderJob handle everything.

What changed:

1. AgentRunnerService now surfaces the handoff_tool_called flag (already
tracked internally for usage metadata) in its response hash.
2. ResponseBuilderJob#handoff_requested? detects handoffs from both V1
(response token) and V2 (tool flag).
3. ResponseBuilderJob#process_response checks handoff_requested? before
the conversation_pending? guard, so V2 handoffs are processed even when
the status has
already changed.
4. ResponseBuilderJob#process_action('handoff') captures
conversation_pending? before calling bot_handoff! and uses that snapshot
to guard both bot_handoff!
and the OOO message - preventing double-execution when V2's HandoffTool
already ran them.

New V2 handoff flow:
AgentRunnerService
  → agent calls HandoffTool (creates private note, calls bot_handoff!)
  → returns response with handoff_tool_called: true

ResponseBuilderJob#process_response
  → handoff_requested? detects the flag
  → process_action('handoff')
    → create_handoff_message (public message for customer)
    → bot_handoff! skipped (conversation_pending? is false)
    → OOO skipped (conversation_pending? is false)

Fixes #13881

## Type of change

Please delete options that are not relevant.

- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality not to work as expected)
- [ ] This change requires a documentation update

## How Has This Been Tested?

- Update existing response_builder_job_spec.rb covering the V2 handoff
path, V2 normal response path, and V1 regression
- Updated existing agent_runner_service_spec.rb expectations for the new
handoff_tool_called key and added a context for when the flag is true

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] 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

---------

Co-authored-by: Aakash Bakhle <48802744+aakashb95@users.noreply.github.com>
Co-authored-by: aakashb95 <aakashbakhle@gmail.com>

enterprise/app/services/captain/assistant/agent_runner_service.rb

@@ -24,6 +24,7 @@ class Captain::Assistant::AgentRunnerService
     @conversation = conversation
     @callbacks = callbacks
     @source = source
+    @handoff_tool_called = false
   end
 
   def generate_response(message_history: [])
@@ -98,13 +99,15 @@ class Captain::Assistant::AgentRunnerService
     output = result.output
     response = output.is_a?(Hash) ? output.with_indifferent_access : { 'response' => output.to_s, 'reasoning' => 'Processed by agent' }
     response['agent_name'] = result.context&.dig(:current_agent)
+    response['handoff_tool_called'] = result.context&.dig(:captain_v2_handoff_tool_called) || false
     response
   end
 
   def error_response(error_message)
     {
       'response' => 'conversation_handoff',
-      'reasoning' => "Error occurred: #{error_message}"
+      'reasoning' => "Error occurred: #{error_message}",
+      'handoff_tool_called' => @handoff_tool_called
     }
   end
 
@@ -175,16 +178,18 @@ class Captain::Assistant::AgentRunnerService
   end
 
   def add_usage_metadata_callback(runner)
-    return runner unless ChatwootApp.otel_enabled?
-
     handoff_tool_name = Captain::Tools::HandoffTool.new(@assistant).name
 
+    # Tool tracking always runs — process_response in the job consumes the resulting
+    # handoff_tool_called flag regardless of whether OTEL is enabled.
     runner.on_tool_complete do |tool_name, _tool_result, context_wrapper|
       track_handoff_usage(tool_name, handoff_tool_name, context_wrapper)
     end
 
-    runner.on_run_complete do |_agent_name, _result, context_wrapper|
-      write_credits_used_metadata(context_wrapper)
+    if ChatwootApp.otel_enabled?
+      runner.on_run_complete do |_agent_name, _result, context_wrapper|
+        write_credits_used_metadata(context_wrapper)
+      end
     end
     runner
   end
@@ -193,15 +198,17 @@ class Captain::Assistant::AgentRunnerService
     return unless context_wrapper&.context
     return unless tool_name.to_s == handoff_tool_name
 
+    # Mirror the flag onto the instance so error_response can surface it even when
+    # the runner raises before returning a result (the context is unreachable then).
     context_wrapper.context[:captain_v2_handoff_tool_called] = true
+    @handoff_tool_called = true
   end
 
   def write_credits_used_metadata(context_wrapper)
     root_span = context_wrapper&.context&.dig(:__otel_tracing, :root_span)
     return unless root_span
 
-    credit_used = !context_wrapper.context[:captain_v2_handoff_tool_called]
-    root_span.set_attribute(format(ATTR_LANGFUSE_METADATA, 'credit_used'), credit_used.to_s)
+    root_span.set_attribute(format(ATTR_LANGFUSE_METADATA, 'credit_used'), @handoff_tool_called ? 'false' : 'true')
   end
 
   def runner