fix: clear the little todos (#58)

* fix: clear the little todos

本轮把 14 卷 TODO 里堆积的一批 quick 级缺口一次清掉，共 9 项，并同步英文翻译。

正确性修复:
- vol4/05-spaceship-operator「坑1」: 旧结论「只写 <=> 不写 == 会编译错误」已过时
  （P1185 后 defaulted <=> 隐式生成 ==，g++ 16.1.1 / clang 22.1.6 双编译器实测）。
  改写为真实会踩的坑「默认 == 不会反向生成 <=>」，附双编译器实测输出。
- vol9 once_callback: enum Status 补 : uint8_t（与正文一致）、补 <cstdint>/<memory>、
  测试计数笔误 11→12（实测源码确为 12 个 TEST_CASE）、裸代码块补语言标记。

内容补充与交叉链接:
- vol2: constexpr-ctor frontmatter 补 C++20、第五节标题「(C++20 预告)」→「(C++20)」；
  udl-basics 补「小结」。
- vol5: ch09 两篇加「概念导览」标注；补三条跨卷链接（ch06→卷四协程、
  ch08→卷六性能、ch03→卷八中断安全）。
- vol10: 6 处行内代码路径改为可点的 GitHub blob 链接；汇编系列 3 篇加延伸阅读
  （卷六 AVX/AVX2、卷七 编译器选项）。

导航与结构整理:
- projects/index 从空壳升级为可用导航页（4 条跨卷/外链 + 近期/规划项目）。
- vol8 嵌入式补 00/01/02 三个目录的 index.md；embedded/index 去掉「规划中」、
  纳入四系列入口。
- 卷八删除冗余 06-array-vs-raw-arrays（卷三 01-array 已覆盖）；EBO 从
  embedded(stm32f1) 迁到 vol4(host)，CN/EN 全链路同步。
- vol1 c_tutorials 49 处「// TODO:」统一改为「// 练习：」，消除规划噪音。

治理:
- todo/000、todo/031 勾掉已完成的验收项；修正 091 stale 引用。

英文同步:
- 用 translate.py(glm-4.6) 同步本轮改动文件的英文镜像，并重译修复 ch07
  被污染成广告内容的英文镜像. (LLM翻译还是要指日可待啊)

* ci: fix the read time issue of en version

Author: Charliechen114514

README.md

@@ -19,7 +19,7 @@
 ---
 
 <!-- COVERAGE_START -->
-![English Coverage](https://img.shields.io/badge/en_coverage-99%25-green.svg) 428/431 docs translated
+![English Coverage](https://img.shields.io/badge/en_coverage-99%25-green.svg) 430/433 docs translated
 <!-- COVERAGE_END -->
 
 ## 这是什么项目

code/volumn_codes/vol9/chrome_design/once_callback/once_callback.hpp

@@ -11,7 +11,9 @@
 
 #pragma once
 #include "cancel_token/cancel_token.hpp"
+#include <cstdint>
 #include <functional>
+#include <memory>
 
 namespace tamcpp::chrome {
 
@@ -38,7 +40,7 @@ class OnceCallback<ReturnType(FuncArgs...)> // Specialization of Functional like
     using FuncSig = ReturnType(FuncArgs...);
 
   private:
-    enum class Status {
+    enum class Status : uint8_t {
         kEmpty,   // Null when construction with no lambda or func specified
         kValid,   // validate for usage
         kConsumed // Has been callbacked
@@ -97,8 +99,10 @@ class OnceCallback<ReturnType(FuncArgs...)> // Specialization of Functional like
      * @return false
      */
     [[nodiscard]] bool is_cancelled() const noexcept {
-        if (status_ != Status::kValid) return true;
-        if (token_ && !token_->is_valid()) return true;
+        if (status_ != Status::kValid)
+            return true;
+        if (token_ && !token_->is_valid())
+            return true;
         return false;
     }
     [[nodiscard]] bool maybe_valid() const noexcept { return !is_cancelled(); }

documents/en/projects/index.md

@@ -1,34 +1,39 @@
 ---
-title: End-to-End Hands-On Project
-description: Handwritten STL, HTTP server, GUI framework, embedded OS, and other comprehensive
-  projects
+title: Comprehensive Hands-on Project
+description: Synthesize scattered knowledge from various volumes into complete projects—from
+  coroutine servers, mini runtimes, to industrial-grade component analysis.
 platform: host
 tags:
 - cpp-modern
 - host
 - intermediate
 translation:
   source: documents/projects/index.md
-  source_hash: 3a6ccce746db47489eb825a9ddde30ec4ba65e96ff42697b0adc3c93c6be84df
-  translated_at: '2026-05-26T10:20:16.450396+00:00'
+  source_hash: 42eb53b42495d01aa1fb318f2084582052831d6c383d0cf22598181cb3c8fd75
+  translated_at: '2026-06-13T11:40:38.476774+00:00'
   engine: anthropic
-  token_count: 106
+  token_count: 324
 ---
 # Comprehensive Hands-on Projects
 
-> Status: Planned
+> This section is not merely a pile of new concepts, but an effort to weave together the fragments learned across various volumes—concurrency, coroutines, templates, memory management—into a complete project that runs, tests, and can be delivered. Below, we first list projects that have already been implemented in other volumes and are ready for you to continue, followed by long-term goals still in the planning phase.
 
-## Overview
+## Projects with a Foundation
 
-This section features comprehensive hands-on projects that span the entire tutorial:
+These projects already have tutorials or runnable skeletons in other volumes, providing a path for you to dive deeper:
 
-1. **Hand-rolled STL Components**: vector, string, unique_ptr, optional, function, variant
-2. **Mini HTTP Server**: from TCP to asynchronous coroutines
-3. **Mini GUI Framework**: event loop, widget system, layout engine, rendering backend
-4. **Embedded Operating System**: scheduler, synchronization primitives, memory management, driver framework
-5. **INI Parser** (basic version available)
-6. **Coroutine Echo Server** (basic version available)
+- **Coroutine Echo Server**: In [Volume 5: Coroutine Echo Server](../vol5-concurrency/ch06-async-io-coroutine/05-coroutine-echo-server.md), we built a fully functional echo service from `io_uring` to data transmission. This is the most practical project for understanding coroutine scheduling.
+- **Mini Concurrent Runtime (Capstone)**: [Volume 5: Mini Runtime Capstone](../vol5-concurrency/exercises/06-capstone-mini-runtime.md) combines thread pools, timers, and task queues into a minimal scheduler, serving as a ready-made starting point for the "Mini Concurrent Runtime".
+- **OnceCallback Component Study**: [Volume 9: OnceCallback](../vol9-open-source-project-learn/chrome/01_once_callback/index.md) dissects Chromium's callback mechanism across 16 articles, serving as a paradigm for transitioning from reading source code to designing industrial-grade components yourself.
+- **INI Parser**: As the first complete project for C++ engineering, this is located in a separate repository [Tutorial_cpp_SimpleIniParser](https://github.com/Awesome-Embedded-Learning-Studio/Tutorial_cpp_SimpleIniParser)—covering lexical analysis to error handling, it is perfect for following along from start to finish.
 
-## Project Navigation
+## Planned Projects
 
-> Content is being written, stay tuned.
+These have not yet started and are long-term goals, sorted by "readiness of materials":
+
+- **Hand-rolled STL Components**: Implement `vector`, `string`, `unique_ptr`, `optional`, `function`, and `variant` from scratch, complementing the source code reading in Volume 3 (Standard Library).
+- **Mini HTTP Server**: From TCP sockets to coroutine-based asynchrony, building upon Volume 5 (Concurrency) and Volume 8 (Network Programming).
+- **Mini GUI Framework**: Event loops, widget systems, layout engines, and rendering backends.
+- **Embedded Mini OS**: Scheduler, synchronization primitives, memory management, and driver framework, extending the main thread of Volume 8 (Embedded Systems).
+
+> These projects will not be completed overnight; they will be launched gradually as the content in their respective volumes is finalized. If you have a project you would like to see, feel free to propose it in the Discussions.