Add the Model Context Protocol Server integration (#134122)

* Add the Model Context Protocol Server integration

* Remove unusued code in init

* Fix comment wording

* Use util.uild for unique ids

* Set config entry title to the LLM API name

* Extract an SSE parser and update comments

* Update comments and defend against already closed sessions

* Shorten description

* Update homeassistant/components/mcp_server/__init__.py

Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>

* Change integration type to service

---------

Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>

tests/components/mcp_server/conftest.py

@@ -0,0 +1,35 @@
+"""Common fixtures for the Model Context Protocol Server tests."""
+
+from collections.abc import Generator
+from unittest.mock import AsyncMock, patch
+
+import pytest
+
+from homeassistant.components.mcp_server.const import DOMAIN
+from homeassistant.const import CONF_LLM_HASS_API
+from homeassistant.core import HomeAssistant
+from homeassistant.helpers import llm
+
+from tests.common import MockConfigEntry
+
+
+@pytest.fixture
+def mock_setup_entry() -> Generator[AsyncMock]:
+    """Override async_setup_entry."""
+    with patch(
+        "homeassistant.components.mcp_server.async_setup_entry", return_value=True
+    ) as mock_setup_entry:
+        yield mock_setup_entry
+
+
+@pytest.fixture(name="config_entry")
+def mock_config_entry(hass: HomeAssistant) -> MockConfigEntry:
+    """Fixture to load the integration."""
+    config_entry = MockConfigEntry(
+        domain=DOMAIN,
+        data={
+            CONF_LLM_HASS_API: llm.LLM_API_ASSIST,
+        },
+    )
+    config_entry.add_to_hass(hass)
+    return config_entry