style: modernize sample code and tame clang-tidy noise

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

@@ -4,18 +4,18 @@
 
 namespace project {
 
-std::string Greeter::greet(const std::string &name) const {
-    return base_message_ + ", " + name + "!";
-}
-
-std::vector<int> generate_sequence(int limit) {
-    if (limit < 0) {
-        limit = 0;
+auto Greeter::greet(const std::string &name) const -> std::string {
+        return base_message_ + ", " + name + "!";
     }
 
-    std::vector<int> result(static_cast<std::size_t>(limit));
-    std::iota(result.begin(), result.end(), 0);
-    return result;
-}
+auto generate_sequence(int limit) -> std::vector<int> {
+        if (limit < 0) {
+            limit = 0;
+        }
 
-}  // namespace project
+        std::vector<int> result(static_cast<std::size_t>(limit));
+        std::iota(result.begin(), result.end(), 0);
+        return result;
+    }
+
+} // namespace project