AI Task integration (#145128)

* Add AI Task integration

* Remove GenTextTaskType

* Add AI Task prefs

* Add action to LLM task

* Remove WS command

* Rename result to text for GenTextTaskResult

* Apply suggestions from code review

Co-authored-by: Allen Porter <allen.porter@gmail.com>

* Add supported feature for generate text

* Update const.py

Co-authored-by: HarvsG <11440490+HarvsG@users.noreply.github.com>

* Update homeassistant/components/ai_task/services.yaml

Co-authored-by: HarvsG <11440490+HarvsG@users.noreply.github.com>

* Use WS API to set preferences

* Simplify pref storage

* Simplify pref test

* Update homeassistant/components/ai_task/services.yaml

Co-authored-by: Allen Porter <allen.porter@gmail.com>

---------

Co-authored-by: Allen Porter <allen.porter@gmail.com>
Co-authored-by: HarvsG <11440490+HarvsG@users.noreply.github.com>

homeassistant/components/ai_task/const.py

@@ -0,0 +1,29 @@
+"""Constants for the AI Task integration."""
+
+from __future__ import annotations
+
+from enum import IntFlag
+from typing import TYPE_CHECKING
+
+from homeassistant.util.hass_dict import HassKey
+
+if TYPE_CHECKING:
+    from homeassistant.helpers.entity_component import EntityComponent
+
+    from . import AITaskPreferences
+    from .entity import AITaskEntity
+
+DOMAIN = "ai_task"
+DATA_COMPONENT: HassKey[EntityComponent[AITaskEntity]] = HassKey(DOMAIN)
+DATA_PREFERENCES: HassKey[AITaskPreferences] = HassKey(f"{DOMAIN}_preferences")
+
+DEFAULT_SYSTEM_PROMPT = (
+    "You are a Home Assistant expert and help users with their tasks."
+)
+
+
+class AITaskEntityFeature(IntFlag):
+    """Supported features of the AI task entity."""
+
+    GENERATE_TEXT = 1
+    """Generate text based on instructions."""