perf(asr): speed up local Flow dictation and land CLM/keyboard refactor

Reduce perceived latency from key release to final text:
- Adaptive chunking: 2.5s first chunk + 5s follow-ups so short
  utterances start on-device recognition while still recording.
- Session-level ASR warmup and audio-format cache reuse to remove
  per-utterance cold-start of SpeechAnalyzer.
- Mirror live pipelined partials to the keyboard transcript line via
  a new flow.transcriptionPartial App Group key + Darwin ping.

Also commits the accumulated custom language model, Flow session,
keyboard extension restructure, and Xiaomi MiMo provider work in
progress on this branch.

CHANGELOG.md

@@ -8,6 +8,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
+- **Xiaomi MiMo cloud provider**: preset for the cloud engine with `mimo-v2.5` polish via `api.xiaomimimo.com` (on-device ASR, same pipeline as other online providers). / **小米 MiMo 云端引擎**：云端引擎新增预设，经 `api.xiaomimimo.com` 使用 `mimo-v2.5` 润色（端侧 ASR，与其他在线服务相同管线）。
+
+### Changed
+- **Flow ASR pipelining**: shorter first chunk (2.5s) and 5s follow-ups so short utterances start on-device recognition while still recording; session-level ASR warmup and format cache reuse; live partials mirrored to the keyboard transcript line. / **Flow ASR 流水线**：首块 2.5 秒、后续 5 秒，短句录音期间即开始端侧识别；会话级 ASR 预热与格式缓存复用；实时 partial 同步到键盘转写行。
+
+## [0.4.0] - 2026-07-05
+
+### Added
+- **Custom ASR language model**: on-device `SFCustomLanguageModelData` bias model (computer/IT terms + curated AI/tech brands) prepared via `CustomLanguageModelManager` and applied to `DictationTranscriber` for Chinese dictation; compiled LM/Vocab shared through the App Group. / **自定义语音识别语言模型**：端侧 `SFCustomLanguageModelData` 偏置模型（计算机术语 + 精选 AI/科技品牌词），通过 `CustomLanguageModelManager` 在设备上准备并挂载到 `DictationTranscriber` 用于中文听写；编译后的 LM/Vocab 经 App Group 共享。
 - **Cursor navigation**: keyboard drag pad (`CursorDragPad` / `CursorNavigation`) for precise caret movement. / **光标导航**：键盘拖动手势区（`CursorDragPad` / `CursorNavigation`），精确移动光标。
 - **Key sound feedback**: `KeyboardSoundFeedback` plays system key clicks on input. / **按键音反馈**：`KeyboardSoundFeedback` 在输入时播放系统按键音。
 - **Personal dictionary tooling**: `DictionaryAliasGenerator` and `PersonalDictionaryEntrySheet` for managing custom terms and aliases. / **个人词库工具**：`DictionaryAliasGenerator` 与 `PersonalDictionaryEntrySheet`，用于管理自定义词条与别名。