Follow-up to the salvaged #56724: the runtime's _generate_xai_tts reads
voice_id, language, speed, auto_speech_tags, optimize_streaming_latency,
sample_rate, and bit_rate — but never text_normalization, and the xAI
/v1/tts payload builder has no such field. Surfacing it in the desktop
GUI would be a dead knob, so remove it from DEFAULT_CONFIG, constants.ts
(labels/descriptions/SECTIONS), and the ja/zh/zh-hant locale catalogs.
The other six xAI keys are all verified against tools/tts_tool.py.
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