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.

OSGKeyboardExt/Services/KeyboardTextInserter.swift

@@ -0,0 +1,44 @@
+// KeyboardTextInserter.swift
+// OSGKeyboard · Keyboard Extension
+//
+// Inserts Flow transcripts from the host app and surfaces polish warnings
+// without re-running LLM polish in the extension.
+
+import OSGKeyboardShared
+
+@MainActor
+final class KeyboardTextInserter {
+    private let state: KeyboardState
+    private let insertText: (String) -> Void
+    private let scheduleAutoClearError: () -> Void
+
+    init(
+        state: KeyboardState,
+        insertText: @escaping (String) -> Void,
+        scheduleAutoClearError: @escaping () -> Void
+    ) {
+        self.state = state
+        self.insertText = insertText
+        self.scheduleAutoClearError = scheduleAutoClearError
+    }
+
+    func handleFlowTranscript(_ delivery: TranscriptionDelivery) {
+        let trimmed = delivery.text.trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !trimmed.isEmpty else {
+            state.phase = .idle
+            state.level = 0
+            return
+        }
+        // Host app already polished when configured; keyboard only inserts.
+        insertText(trimmed)
+        state.lastTranscript = ""
+        state.level = 0
+        if let warning = delivery.polishWarning {
+            state.phase = .error(.polishDegraded(warning), message: warning)
+            scheduleAutoClearError()
+        } else {
+            state.phase = .idle
+        }
+        OSGLog.keyboardExt.info("flow insert length=\(trimmed.count, privacy: .public)")
+    }
+}