Add conversation entity (#114518)

* Default agent as entity

* Migrate constant to point at new value

* Fix tests

* Fix more tests

* Move assist pipeline back to cloud after dependenceis

tests/components/openai_conversation/conftest.py

@@ -4,6 +4,7 @@ from unittest.mock import patch
 
 import pytest
 
+from homeassistant.core import HomeAssistant
 from homeassistant.setup import async_setup_component
 
 from tests.common import MockConfigEntry
@@ -30,3 +31,9 @@ async def mock_init_component(hass, mock_config_entry):
     ):
         assert await async_setup_component(hass, "openai_conversation", {})
         await hass.async_block_till_done()
+
+
+@pytest.fixture(autouse=True)
+async def setup_ha(hass: HomeAssistant) -> None:
+    """Set up Home Assistant."""
+    assert await async_setup_component(hass, "homeassistant", {})