feat(asr): Add Cohere Transcribe with INT8 support

Sources/FluidAudio/ASR/Cohere/CohereAsrConfig.swift

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+import Foundation
+
+/// Configuration for Cohere Transcribe CoreML ASR model.
+public enum CohereAsrConfig {
+    /// Sample rate expected by the model (16kHz).
+    public static let sampleRate: Int = 16000
+
+    /// Maximum audio duration in seconds (30s).
+    public static let maxAudioSeconds: Float = 30.0
+
+    /// Maximum number of audio samples (480,000 at 16kHz = 30 seconds).
+    public static let maxSamples: Int = 480_000
+
+    /// Vocabulary size.
+    public static let vocabSize: Int = 16_384
+
+    /// Encoder hidden size (Conformer blocks).
+    public static let encoderHiddenSize: Int = 1280
+
+    /// Decoder hidden size.
+    public static let decoderHiddenSize: Int = 1024
+
+    /// Number of encoder layers.
+    public static let numEncoderLayers: Int = 48
+
+    /// Number of decoder layers.
+    public static let numDecoderLayers: Int = 8
+
+    /// Number of attention heads in decoder.
+    public static let numDecoderHeads: Int = 8
+
+    /// Head dimension (1024 / 8).
+    public static let headDim: Int = 128
+
+    /// Maximum sequence length for decoder KV cache.
+    public static let maxSeqLen: Int = 108
+
+    /// Number of mel bins.
+    public static let numMelBins: Int = 128
+
+    /// Mel spectrogram parameters.
+    public enum MelSpec {
+        public static let nFFT: Int = 1024
+        public static let hopLength: Int = 160
+        public static let nMels: Int = 128
+        public static let fMin: Float = 0.0
+        public static let fMax: Float = 8000.0
+        public static let preemphasis: Float = 0.97
+    }
+
+    /// Special tokens.
+    public enum SpecialTokens {
+        /// Unknown token.
+        public static let unkToken: Int = 0
+        /// No speech token.
+        public static let noSpeechToken: Int = 1
+        /// Padding token.
+        public static let padToken: Int = 2
+        /// End of text / End of sequence token.
+        public static let eosToken: Int = 3
+        /// Start of transcript token.
+        public static let startToken: Int = 4
+        /// Start of context token.
+        public static let startOfContext: Int = 7
+        /// Emotion undefined token.
+        public static let emoUndefined: Int = 16
+        /// Punctuation token.
+        public static let pnc: Int = 5
+        /// No inverse text normalization.
+        public static let noitn: Int = 9
+        /// No timestamp token.
+        public static let notimestamp: Int = 11
+        /// No diarization token.
+        public static let nodiarize: Int = 13
+        /// Word boundary marker.
+        public static let wordBoundary: Int = 13764
+    }
+
+    /// Supported languages.
+    public enum Language: String, CaseIterable, Sendable {
+        case english = "en"
+        case french = "fr"
+        case german = "de"
+        case spanish = "es"
+        case italian = "it"
+        case portuguese = "pt"
+        case dutch = "nl"
+        case polish = "pl"
+        case greek = "el"
+        case arabic = "ar"
+        case japanese = "ja"
+        case chinese = "zh"
+        case vietnamese = "vi"
+        case korean = "ko"
+
+        public var englishName: String {
+            switch self {
+            case .english: return "English"
+            case .french: return "French"
+            case .german: return "German"
+            case .spanish: return "Spanish"
+            case .italian: return "Italian"
+            case .portuguese: return "Portuguese"
+            case .dutch: return "Dutch"
+            case .polish: return "Polish"
+            case .greek: return "Greek"
+            case .arabic: return "Arabic"
+            case .japanese: return "Japanese"
+            case .chinese: return "Chinese"
+            case .vietnamese: return "Vietnamese"
+            case .korean: return "Korean"
+            }
+        }
+
+        /// Language token ID (used as start token for conditioned generation).
+        public var tokenId: Int {
+            switch self {
+            case .english: return 62
+            case .french: return 69
+            case .german: return 76
+            case .spanish: return 169
+            case .italian: return 97
+            case .portuguese: return 149
+            case .dutch: return 60
+            case .polish: return 148
+            case .greek: return 77
+            case .arabic: return 28
+            case .japanese: return 98
+            case .chinese: return 50
+            case .vietnamese: return 194
+            case .korean: return 110
+            }
+        }
+
+        /// Build the prompt sequence for this language.
+        ///
+        /// Cohere models expect a specific prompt sequence:
+        /// 1. Word boundary marker
+        /// 2. Start of context
+        /// 3. Start of transcript
+        /// 4. Emotion undefined
+        /// 5-6. Language token (repeated twice)
+        /// 7. Punctuation
+        /// 8. No inverse text normalization
+        /// 9. No timestamp
+        /// 10. No diarization
+        public var promptSequence: [Int] {
+            let langToken = tokenId
+            return [
+                SpecialTokens.wordBoundary,  // ▁
+                SpecialTokens.startOfContext,  // <|startofcontext|>
+                SpecialTokens.startToken,  // <|startoftranscript|>
+                SpecialTokens.emoUndefined,  // <|emo:undefined|>
+                langToken,  // <|en|> (or other language)
+                langToken,  // <|en|> (repeated)
+                SpecialTokens.pnc,  // <|pnc|>
+                SpecialTokens.noitn,  // <|noitn|>
+                SpecialTokens.notimestamp,  // <|notimestamp|>
+                SpecialTokens.nodiarize,  // <|nodiarize|>
+            ]
+        }
+    }
+}