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/ModelStoreDownloadSupportTests.swift

@@ -0,0 +1,92 @@
+import Testing
+import Foundation
+@testable import 康康
+
+struct ModelStoreDownloadSupportTests {
+
+    private func isolatedStore() throws -> ModelStore {
+        let temp = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString, isDirectory: true)
+        return try ModelStore(rootURL: temp)
+    }
+
+    @Test func fileURLPointsIntoModelFolder() throws {
+        let store = try isolatedStore()
+        defer { try? FileManager.default.removeItem(at: store.rootURL) }
+        let url = store.fileURL(for: .llm, relativePath: "config.json")
+        #expect(url == store.localURL(for: .llm).appendingPathComponent("config.json"))
+    }
+
+    @Test func localBytesZeroWhenMissing() throws {
+        let store = try isolatedStore()
+        defer { try? FileManager.default.removeItem(at: store.rootURL) }
+        #expect(store.localBytes(for: .llm, relativePath: "config.json") == 0)
+    }
+
+    @Test func localBytesReturnsFileSize() throws {
+        let store = try isolatedStore()
+        defer { try? FileManager.default.removeItem(at: store.rootURL) }
+        let folder = store.localURL(for: .llm)
+        try FileManager.default.createDirectory(at: folder, withIntermediateDirectories: true)
+        try Data(repeating: 7, count: 512).write(to: folder.appendingPathComponent("config.json"))
+        #expect(store.localBytes(for: .llm, relativePath: "config.json") == 512)
+    }
+
+    @Test func isCompleteFalseWhenFilesMissing() throws {
+        let store = try isolatedStore()
+        defer { try? FileManager.default.removeItem(at: store.rootURL) }
+        let files = [ModelFile(path: "a.bin", bytes: 1024)]
+        #expect(store.isComplete(for: .llm, files: files) == false)
+    }
+
+    @Test func isCompleteTrueWhenAllFilesPresentWithExpectedSize() throws {
+        let store = try isolatedStore()
+        defer { try? FileManager.default.removeItem(at: store.rootURL) }
+        let folder = store.localURL(for: .llm)
+        try FileManager.default.createDirectory(at: folder, withIntermediateDirectories: true)
+        try Data(repeating: 1, count: 1024).write(to: folder.appendingPathComponent("a.bin"))
+        let files = [ModelFile(path: "a.bin", bytes: 1024)]
+        #expect(store.isComplete(for: .llm, files: files) == true)
+    }
+
+    @Test func isCompleteFalseWhenSizeMismatch() throws {
+        let store = try isolatedStore()
+        defer { try? FileManager.default.removeItem(at: store.rootURL) }
+        let folder = store.localURL(for: .llm)
+        try FileManager.default.createDirectory(at: folder, withIntermediateDirectories: true)
+        try Data(repeating: 1, count: 999).write(to: folder.appendingPathComponent("a.bin"))
+        let files = [ModelFile(path: "a.bin", bytes: 1024)]
+        #expect(store.isComplete(for: .llm, files: files) == false)
+    }
+
+    @Test func importModelCopiesFolderAndMarksReady() throws {
+        let store = try isolatedStore()
+        defer { try? FileManager.default.removeItem(at: store.rootURL) }
+
+        let src = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString, isDirectory: true)
+        try FileManager.default.createDirectory(at: src, withIntermediateDirectories: true)
+        defer { try? FileManager.default.removeItem(at: src) }
+        try "{}".write(to: src.appendingPathComponent("config.json"), atomically: true, encoding: .utf8)
+        try "x".write(to: src.appendingPathComponent("tokenizer.json"), atomically: true, encoding: .utf8)
+
+        try store.importModel(.llm, from: src)
+
+        #expect(store.isReady(.llm) == true)
+        #expect(FileManager.default.fileExists(
+            atPath: store.fileURL(for: .llm, relativePath: "tokenizer.json").path))
+    }
+
+    @Test func importModelThrowsWhenNoConfig() throws {
+        let store = try isolatedStore()
+        defer { try? FileManager.default.removeItem(at: store.rootURL) }
+        let src = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString, isDirectory: true)
+        try FileManager.default.createDirectory(at: src, withIntermediateDirectories: true)
+        defer { try? FileManager.default.removeItem(at: src) }
+
+        #expect(throws: (any Error).self) {
+            try store.importModel(.llm, from: src)
+        }
+    }
+}