feat(models): 模型自动下载(我的·模型管理) + 断点续传 + 旁路导入

实现 spec(2026-05-29-model-download-design)的模型分发功能:
- ModelManifest: 硬编码功能文件清单 + base URL https://file.myv0.com/
- FileDownloader: URLSessionDataDelegate 分块写盘,HTTP Range 断点续传 + 大小校验
  (根因修复:URL.resourceValues 会缓存文件大小,续传时先读 offset 再读 finalSize
   会拿到下载前的陈旧值导致校验误判;改用 FileManager.attributesOfItem)
- ModelDownloadService: @MainActor @Observable 编排逐文件下载,聚合进度/速度,
  支持下载全部/暂停/重试,以及旁路文件导入
- ModelStore: 新增 fileURL/localBytes/isComplete(可注入清单)/importModel(补 VL)
- ModelManagementView: 分模型卡片(状态/进度/速度) + 下载全部/暂停
  + NWPathMonitor 蜂窝提示 + 从文件导入(离线兜底)
- MeView: 模型管理卡改 NavigationLink + 动态状态(已就绪/下载中/N就绪)

测试(Swift Testing): Manifest 清单/字节数、Store 路径/校验/导入、
DownloadState、FileDownloader(URLProtocol mock:下载/Range续传/大小校验)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

康康Tests/ModelManifestTests.swift

@@ -0,0 +1,47 @@
+import Testing
+import Foundation
+@testable import 康康
+
+struct ModelManifestTests {
+
+    @Test func llmHasNineFunctionalFiles() {
+        #expect(ModelManifest.files(for: .llm).count == 9)
+    }
+
+    @Test func vlHasElevenFunctionalFiles() {
+        #expect(ModelManifest.files(for: .vl).count == 11)
+    }
+
+    @Test func llmTotalBytesMatchesManifest() {
+        #expect(ModelManifest.totalBytes(for: .llm) == 984_013_244)
+    }
+
+    @Test func vlTotalBytesMatchesManifest() {
+        #expect(ModelManifest.totalBytes(for: .vl) == 3_089_710_883)
+    }
+
+    @Test func excludesReadmeAndGitattributes() {
+        for kind in [ModelKind.llm, .vl] {
+            let names = ModelManifest.files(for: kind).map(\.path)
+            #expect(!names.contains("README.md"))
+            #expect(!names.contains(".gitattributes"))
+        }
+    }
+
+    @Test func includesEssentialFiles() {
+        let llm = ModelManifest.files(for: .llm).map(\.path)
+        #expect(llm.contains("config.json"))
+        #expect(llm.contains("model.safetensors"))
+        #expect(llm.contains("tokenizer.json"))
+
+        let vl = ModelManifest.files(for: .vl).map(\.path)
+        #expect(vl.contains("preprocessor_config.json"))  // VL 拍照识别必需
+        #expect(vl.contains("model.safetensors"))
+    }
+
+    @Test func fileURLIsBaseSlashRepoSlashPath() {
+        let file = ModelFile(path: "config.json", bytes: 937)
+        let url = ModelManifest.fileURL(for: .llm, file: file)
+        #expect(url.absoluteString == "https://file.myv0.com/Qwen3-1.7B-4bit/config.json")
+    }
+}