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.

OSGKeyboardShared/Models/EngineServiceLabel.swift

@@ -10,12 +10,11 @@ public enum EngineServiceLabel {
         engineMode: String,
         providerId: String,
         model: String,
-        localASRBackend: LocalASRBackend = .speechAnalyzer,
         language: AppUILanguage? = nil
     ) -> String {
         let lang = language ?? AppGroupStore().uiLanguage
         if engineMode == "local" {
-            let asrName = asrDisplayName(for: localASRBackend, language: lang)
+            let asrName = SharedL10n.string("engine.asr.appleSpeech", language: lang)
             return SharedL10n.format("engine.summary.local", language: lang, asrName)
         }
         let providerName = ProviderDisplayName.name(for: providerId, language: lang)
@@ -30,14 +29,4 @@ public enum EngineServiceLabel {
             trimmedModel
         )
     }
-
-    private static func asrDisplayName(
-        for backend: LocalASRBackend,
-        language: AppUILanguage
-    ) -> String {
-        // v0.2.0: only the iOS SpeechAnalyzer path remains. We keep the
-        // switch on `LocalASRBackend` so the next non-iOS backend can
-        // slot in without touching every call site.
-        return SharedL10n.string("engine.asr.appleSpeech", language: language)
-    }
-}
+}