Add Makefile and reference it in guidelines

AGENTS.md

@@ -94,8 +94,9 @@ This repository is written in Rust and uses Cargo for building and dependency
 management. Contributors should follow these best practices when working on the
 project:
 
-- Run cargo fmt, cargo clippy -- -D warnings, and RUSTFLAGS="-D warnings" cargo
-  test before committing.
+- Run `make fmt`, `make lint`, and `make test` before committing. These targets
+  wrap `cargo fmt`, `cargo clippy`, and `cargo test` with the appropriate
+  flags.
 - Clippy warnings MUST be disallowed.
 - Fix any warnings emitted during tests in the code itself rather than
   silencing them.

Makefile

@@ -0,0 +1,17 @@
+.PHONY: lint test fmt
+
+# Run Clippy lints across all targets and features, failing on warnings
+lint:
+	cargo clippy --all-targets --all-features -- -D warnings
+
+# Execute tests with warnings treated as errors
+# --quiet ensures less verbose output on success
+# Use RUSTFLAGS to deny warnings at compile time
+# so new warnings cause failures
+
+test:
+	RUSTFLAGS="-D warnings" cargo test --quiet
+
+# Format the entire workspace
+fmt:
+	cargo fmt --all

tests/lifecycle.rs

@@ -67,7 +67,7 @@ async fn teardown_without_setup_does_not_run() {
 
     let app = WireframeApp::new()
         .unwrap()
-        .on_connection_teardown(move |_| {
+        .on_connection_teardown(move |()| {
             let teardown_clone = teardown_clone.clone();
             async move {
                 teardown_clone.fetch_add(1, Ordering::SeqCst);