Address PR review: rename to XAIHttpTTSService, add language map, clean up API

- Rename XAITTSService → XAIHttpTTSService and XAITTSSettings → XAIHttpTTSSettings
- Add language_to_xai_language() with explicit LANGUAGE_MAP using resolve_language()
- Remove deprecated InputParams, params, voice, language init params
- Remove XAI_DEFAULT_SAMPLE_RATE and XAI_PCM_CODEC constants; add encoding param
- Set sample_rate=None default (picked up from PipelineParams or user)
- Use Language.EN enum instead of string "en" for default language
- Add changelog/4031.added.md
- Add 07e-interruptible-xai.py foundational example
- Update 14g-function-calling-grok.py to use XAIHttpTTSService
- Register 07e in run-release-evals.py

tests/test_xai_tts.py

@@ -4,7 +4,7 @@
 # SPDX-License-Identifier: BSD 2-Clause License
 #
 
-"""Tests for XAITTSService."""
+"""Tests for XAIHttpTTSService."""
 
 import asyncio
 import unittest
@@ -21,7 +21,7 @@ from pipecat.frames.frames import (
     TTSStoppedFrame,
     TTSTextFrame,
 )
-from pipecat.services.xai.tts import XAITTSService
+from pipecat.services.xai.tts import XAIHttpTTSService
 from pipecat.tests.utils import run_test
 
 
@@ -52,7 +52,7 @@ async def test_run_xai_tts_success(aiohttp_client):
     base_url = str(client.make_url("/v1/tts"))
 
     async with aiohttp.ClientSession() as session:
-        tts_service = XAITTSService(
+        tts_service = XAIHttpTTSService(
             api_key="test-key",
             base_url=base_url,
             aiohttp_session=session,