feat: harden Flow cold-start/force-quit and polish macOS dictation UX

Fix cold-start overlay recursion that overflowed the main-thread stack when
recording began while the ready overlay was still up; also remove temporary
on-screen Flow DEBUG panels after the orange-mic investigation, and land the
macOS overlay/catalog/layout polish plus related Flow recovery hardening.

OSGKeyboardShared/Services/ASRService.swift

@@ -30,7 +30,7 @@ extension AVAudioPCMBuffer: @unchecked @retroactive Sendable {}
 
 // MARK: - Protocol
 
-public protocol ASRService: Sendable {
+public protocol ASRService: ASRChunkTranscribing, Sendable {
     /// Start a transcription session. The returned stream emits `.partial`
     /// updates and exactly one `.final` (or `.error`) before finishing.
     /// `SpeechAnalyzer` is always fully on-device, so there is no
@@ -54,12 +54,6 @@ public protocol ASRService: Sendable {
     func transcribeChunk(samples: [Float], locale: Locale) async -> ASRChunkResult
 }
 
-public enum ASRChunkResult: Sendable, Equatable {
-    case success(String)
-    case failure(String)
-    case cancelled
-}
-
 extension ASRService {
     public func resetForNewUtterance() {}