fix(desktop): drop tts.xai.text_normalization — not honored by the xAI TTS backend

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.

apps/desktop/src/app/settings/constants.ts

@@ -387,7 +387,6 @@ export const FIELD_LABELS: Record<string, string> = defineFieldCopy({
       language: 'xAI Language',
       speed: 'xAI Playback Speed',
       autoSpeechTags: 'xAI Auto Speech Tags',
-      textNormalization: 'xAI Text Normalization',
       optimizeStreamingLatency: 'xAI Streaming Latency Optimization',
       sampleRate: 'xAI Sample Rate',
       bitRate: 'xAI Bit Rate'
@@ -500,7 +499,6 @@ export const FIELD_DESCRIPTIONS: Record<string, string> = defineFieldCopy({
       language: 'Spoken language code (e.g. en, pt-BR) or "auto" for auto-detection.',
       speed: 'Playback speed. 0.7 = slower, 1.0 = normal, 1.5 = faster.',
       autoSpeechTags: 'Let an LLM insert expressive audio tags ([laughing], [sighs]) into the script before synthesis.',
-      textNormalization: 'Convert numbers, abbreviations, and symbols to spoken form before synthesis.',
       optimizeStreamingLatency: 'Latency vs. quality trade-off. 0 = best quality, 2 = lowest latency.',
       sampleRate: 'Audio sample rate in Hz. Higher = better quality, larger files.',
       bitRate: 'MP3 bitrate in bps. Only applies when codec is mp3.'
@@ -606,7 +604,6 @@ export const SECTIONS: DesktopConfigSection[] = [
       'tts.xai.language',
       'tts.xai.speed',
       'tts.xai.auto_speech_tags',
-      'tts.xai.text_normalization',
       'tts.xai.optimize_streaming_latency',
       'tts.xai.sample_rate',
       'tts.xai.bit_rate',

apps/desktop/src/i18n/ja.ts

@@ -468,7 +468,6 @@ export const ja = defineLocale({
           language: 'xAI 言語',
           speed: '再生速度',
           autoSpeechTags: '自動音声タグ',
-          textNormalization: 'テキスト正規化',
           optimizeStreamingLatency: 'ストリーミング遅延最適化',
           sampleRate: 'サンプルレート',
           bitRate: 'ビットレート'

apps/desktop/src/i18n/zh-hant.ts

@@ -457,7 +457,6 @@ export const zhHant = defineLocale({
           language: 'xAI 語言',
           speed: '播放速度',
           autoSpeechTags: '自動語音標籤',
-          textNormalization: '文字正規化',
           optimizeStreamingLatency: '串流延遲最佳化',
           sampleRate: '取樣率',
           bitRate: '位元率'

apps/desktop/src/i18n/zh.ts

@@ -568,7 +568,6 @@ export const zh: Translations = {
           language: 'xAI 语言',
           speed: '播放速度',
           autoSpeechTags: '自动语音标签',
-          textNormalization: '文本规范化',
           optimizeStreamingLatency: '流式延迟优化',
           sampleRate: '采样率',
           bitRate: '比特率'