代码审查：改进并发安全与代码质量 / Code Review: Improve Concurrency Safety & Code Quality

## 背景 / Background

在对项目进行代码审查后，发现以下可改进的方面。已实施部分修改并在 #1726 中提交。
After reviewing the project code, the following areas for improvement were identified. Some changes have been implemented in #1726.

## 审查发现 / Findings

### 高优先级 / High Priority
1. **`nonisolated(unsafe)` 使用 / Usage**
- `Application.swift` 中的 `bootstrapLogger` 使用了 `nonisolated(unsafe) var`，可以改用 `Mutex` 保护以符合 Swift 6 严格并发检查
- `bootstrapLogger` in `Application.swift` uses `nonisolated(unsafe) var` — can be replaced with `Mutex` for Swift 6 concurrency safety
- ✅ 已修复 / Fixed

### 中优先级 / Medium Priority
2. **`NSLock` → 现代替代品 / Modern Replacement**
- XPC 模块中的 `NSLock` 用于保护 XPC C 类型（`xpc_object_t`、`xpc_connection_t`）
- `NSLock` in XPC modules protects non-Sendable XPC C types (`xpc_object_t`, `xpc_connection_t`)
- ❌ 保留 / Retained: `Mutex`/`OSAllocatedUnfairLock` 的 `@Sendable` 闭包与这些 C 类型不兼容 / Their `@Sendable` closures are incompatible with these C types

### 低优先级 / Low Priority
3. **硬编码端口 / Hardcoded Ports**
- `APIServer+Start.swift` 中的端口号和地址是硬编码的
- Port numbers and addresses in `APIServer+Start.swift` are hardcoded
- ✅ 已修复 / Fixed

4. **C 风格错误处理 / C-Style Error Handling**
- `ContainerRun.swift` 中 `cidfile` 创建使用了 `errno`
- `cidfile` creation in `ContainerRun.swift` uses `errno`
- ✅ 已修复 / Fixed

5. **测试覆盖率 / Test Coverage**
- 核心业务逻辑（`ContainerResource`、`ContainerXPC` 等）的单元测试覆盖率可提升
- Unit test coverage for core business logic (`ContainerResource`, `ContainerXPC`, etc.) could be improved
- ⏳ 待办 / Todo

## 已提交的 PR / Submitted PR
- #1726 - 实现了第 1、3、4 项改进 / Implements improvements 1, 3, and 4

Start by reviewing the remaining findings after #1726, especially the XPC modules and the unit-test coverage for ContainerResource and ContainerXPC. Read Application.swift, APIServer+Start.swift, and ContainerRun.swift to distinguish completed work from open work. Done means the remaining actionable concurrency or coverage gaps are identified and covered by tests.

Written by the indexing model from the issue text.