## Description

The `/v1/responses` endpoint returns responses with `"object": "chat.completion"` instead of the OpenAI Responses API spec value `"object": "response"`.

## Root Cause

In `litellm/responses/litellm_completion_transformation/transformation.py` line 1645:

```python object=chat_completion_response.object, ```

This directly copies the internal Chat Completions response's `object` field rather than setting it to `"response"` for the Responses API response envelope.

## Expected Behavior

OpenAI's Responses API returns `"object": "response"` in the top-level response. The LiteLLM Responses API endpoint should match this.

## Actual Behavior

`"object": "chat.completion"` is returned, which breaks strict clients (e.g., OpenAI Codex CLI with `wire_api = "responses"`) that validate the response envelope.

## Steps to Reproduce

1. Start LiteLLM proxy with any model 2. Send a request to `/v1/responses` 3. Observe `"object": "chat.completion"` in the response

## Fix

```diff - object=chat_completion_response.object, + object="response", ```

Also need to clear `__pycache__` for the change to take effect.

## Related

Also noted in issue #11204 but was not fixed by the asso…