Prefer FP32 over INT8 for Streaming Paraformer when available

If user downloads from GitHub (999MB full package), use FP32 version
for better accuracy. Fall back to INT8 if only INT8 is available
(e.g., from ModelScope's optimized 216MB package).

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ZhaoChaoqun

Sources/SherpaOnnxManager.swift

@@ -133,20 +133,37 @@ class SherpaOnnxManager: NSObject {
 
     // MARK: - Streaming Paraformer 模型路径
 
-    /// 获取 Streaming Paraformer 模型路径
+    /// 获取 Streaming Paraformer 模型路径（优先使用 FP32，否则使用 INT8）
     func getStreamingParaformerPath() -> (encoderPath: String, decoderPath: String, tokensPath: String)? {
         let modelDir = modelsDirectory.appendingPathComponent(ASRModelType.streamingParaformer.folderName)
-        let encoderPath = modelDir.appendingPathComponent("encoder.int8.onnx")
-        let decoderPath = modelDir.appendingPathComponent("decoder.int8.onnx")
         let tokensPath = modelDir.appendingPathComponent("tokens.txt")
 
-        guard FileManager.default.fileExists(atPath: encoderPath.path),
-              FileManager.default.fileExists(atPath: decoderPath.path),
-              FileManager.default.fileExists(atPath: tokensPath.path) else {
+        // 检查 tokens.txt 是否存在
+        guard FileManager.default.fileExists(atPath: tokensPath.path) else {
             return nil
         }
 
-        return (encoderPath.path, decoderPath.path, tokensPath.path)
+        // 优先使用 FP32 版本（精度更高）
+        let encoderFP32 = modelDir.appendingPathComponent("encoder.onnx")
+        let decoderFP32 = modelDir.appendingPathComponent("decoder.onnx")
+
+        if FileManager.default.fileExists(atPath: encoderFP32.path),
+           FileManager.default.fileExists(atPath: decoderFP32.path) {
+            print("[SherpaOnnx] 使用 FP32 版本 Streaming Paraformer（精度更高）")
+            return (encoderFP32.path, decoderFP32.path, tokensPath.path)
+        }
+
+        // 回退到 INT8 版本
+        let encoderINT8 = modelDir.appendingPathComponent("encoder.int8.onnx")
+        let decoderINT8 = modelDir.appendingPathComponent("decoder.int8.onnx")
+
+        if FileManager.default.fileExists(atPath: encoderINT8.path),
+           FileManager.default.fileExists(atPath: decoderINT8.path) {
+            print("[SherpaOnnx] 使用 INT8 版本 Streaming Paraformer")
+            return (encoderINT8.path, decoderINT8.path, tokensPath.path)
+        }
+
+        return nil
     }
 
     /// 检查 Streaming Paraformer 模型是否已下载