```

feat(debug): 添加模型导入功能并修复模拟器GPU初始化问题

- 在DebugAIRunner中添加文件导入器，支持用户选择并导入LLM模型文件夹
- 添加导入状态管理和错误提示功能
- 修复iOS模拟器环境下MLX GPU stream初始化崩溃问题，强制使用CPU模式
- 添加UniformTypeIdentifiers导入以支持文件选择功能
```

体己/Debug/DebugAIRunner.swift

@@ -1,6 +1,7 @@
 #if DEBUG
 import SwiftUI
 import UIKit
+import UniformTypeIdentifiers
 
 /// DEBUG 自检:加载 LLM 并跑一段 prompt,流式显示 token + 速率。
 /// 同时显示沙盒 Application Support 路径,方便把模型拷进去。
@@ -10,6 +11,8 @@ struct DebugAIRunner: View {
     @State private var rate: Double = 0
     @State private var running = false
     @State private var modelReady: Bool = false
+    @State private var importingModel = false
+    @State private var importError: String?
 
     private var appSupportPath: String {
         (try? FileManager.default.url(
@@ -47,12 +50,25 @@ struct DebugAIRunner: View {
                     .font(.system(size: 11))
                     .buttonStyle(.borderless)
 
+                    Button(importingModel ? "导入中..." : "导入模型") {
+                        importingModel = true
+                    }
+                    .font(.system(size: 11))
+                    .buttonStyle(.borderless)
+                    .disabled(importingModel)
+
                     Spacer()
 
                     Text(modelReady ? "✓ 模型就绪" : "⚠ 模型未就绪")
                         .font(.system(size: 11, weight: .medium))
                         .foregroundStyle(modelReady ? Tj.Palette.leaf : Tj.Palette.brick)
                 }
+                if let importError {
+                    Text(importError)
+                        .font(.system(size: 10))
+                        .foregroundStyle(Tj.Palette.brick)
+                        .lineLimit(3)
+                }
             }
             .padding(10)
             .background(
@@ -95,12 +111,69 @@ struct DebugAIRunner: View {
         )
         .padding(.horizontal, 16)
         .onAppear { refreshModelStatus() }
+        .fileImporter(
+            isPresented: $importingModel,
+            allowedContentTypes: [.folder],
+            allowsMultipleSelection: false
+        ) { result in
+            importModelFolder(from: result)
+        }
     }
 
     private func refreshModelStatus() {
         modelReady = ModelStore.shared.isReady(.llm)
     }
 
+    private func importModelFolder(from result: Result<[URL], Error>) {
+        defer {
+            refreshModelStatus()
+            importingModel = false
+        }
+
+        do {
+            guard let pickedURL = try result.get().first else {
+                importError = "未选择模型文件夹"
+                return
+            }
+
+            let securityScoped = pickedURL.startAccessingSecurityScopedResource()
+            defer {
+                if securityScoped {
+                    pickedURL.stopAccessingSecurityScopedResource()
+                }
+            }
+
+            let sourceURL = resolvedModelSourceURL(from: pickedURL)
+            guard FileManager.default.fileExists(
+                atPath: sourceURL.appendingPathComponent(ModelKind.llm.sentinelFilename).path
+            ) else {
+                importError = "请选择包含 config.json 的 Qwen3-1.7B-4bit 文件夹"
+                return
+            }
+
+            let targetURL = ModelStore.shared.localURL(for: .llm)
+            let parentURL = targetURL.deletingLastPathComponent()
+            try FileManager.default.createDirectory(at: parentURL, withIntermediateDirectories: true)
+            if FileManager.default.fileExists(atPath: targetURL.path) {
+                try FileManager.default.removeItem(at: targetURL)
+            }
+            try FileManager.default.copyItem(at: sourceURL, to: targetURL)
+            importError = nil
+        } catch {
+            importError = "导入失败:\(error.localizedDescription)"
+        }
+    }
+
+    private func resolvedModelSourceURL(from pickedURL: URL) -> URL {
+        let nestedURL = pickedURL.appendingPathComponent(ModelKind.llm.rawValue, isDirectory: true)
+        if FileManager.default.fileExists(
+            atPath: nestedURL.appendingPathComponent(ModelKind.llm.sentinelFilename).path
+        ) {
+            return nestedURL
+        }
+        return pickedURL
+    }
+
     @MainActor
     private func run() async {
         running = true