style: modernize sample code and tame clang-tidy noise

Makefile

@@ -55,7 +55,7 @@ tidy:
 	@if [ -n "$(strip $(SRCS))" ]; then \
 		for src in $(SRCS); do \
 			echo "running clang-tidy on $$src"; \
-			$(CLANG_TIDY) $$src -- $(CPPFLAGS) $(CXXFLAGS); \
+			$(CLANG_TIDY) -quiet $$src -- $(CPPFLAGS) $(CXXFLAGS); \
 		done; \
 	else \
 		echo "warning: no source files found for clang-tidy"; \

README.md

@@ -82,7 +82,7 @@ CXX=clang++ CXXFLAGS="-std=c++20 -O3" make
 `.clang-tidy` 啟用了一些常用的檢查（`bugprone-*`、`clang-analyzer-*`、`modernize-*` 等）。可使用 `make tidy` 或 `CLANG_TIDY=/path/to/clang-tidy make tidy` 對 `src/*.cpp` 逐一檢查；若要檢查特定檔案，可執行：
 
 ```bash
-clang-tidy src/app/main.cpp -- -Iinclude
+clang-tidy -quiet src/app/main.cpp -- -Iinclude
 ```
 
 可視需求調整 `Checks`、`HeaderFilterRegex` 或其他設定來符合專案需求。

include/project/sample_library.hpp

@@ -10,13 +10,13 @@ class Greeter {
     public:
         explicit Greeter(std::string base = "Hello") : base_message_(std::move(base)) {}
 
-    [[nodiscard]] std::string greet(const std::string &name) const;
+    [[nodiscard]] auto greet(const std::string &name) const -> std::string;
 
     private:
         std::string base_message_;
     };
 
     // generate_sequence returns numbers from 0 up to limit (exclusive).
-[[nodiscard]] std::vector<int> generate_sequence(int limit);
+[[nodiscard]] auto generate_sequence(int limit) -> std::vector<int>;
 
 } // namespace project

src/app/main.cpp

@@ -2,14 +2,15 @@
 
 #include <iostream>
 
-int main() {
+auto main() -> int {
     std::ios::sync_with_stdio(false);
     std::cin.tie(nullptr);
 
     const project::Greeter greeter{"Welcome"};
     std::cout << greeter.greet("Coding World") << '\n';
 
-    auto sequence = project::generate_sequence(5);
+    constexpr int kSampleSequenceLength = 5;
+    auto sequence = project::generate_sequence(kSampleSequenceLength);
     std::cout << "Sample sequence:";
     for (int value : sequence) {
         std::cout << ' ' << value;

src/lib/sample_library.cpp

@@ -4,11 +4,11 @@
 
 namespace project {
 
-std::string Greeter::greet(const std::string &name) const {
+auto Greeter::greet(const std::string &name) const -> std::string {
         return base_message_ + ", " + name + "!";
     }
 
-std::vector<int> generate_sequence(int limit) {
+auto generate_sequence(int limit) -> std::vector<int> {
         if (limit < 0) {
             limit = 0;
         }