Do the Trunk build check as an end-to-end test

This consolidates our whole CI workflow into `cargo test`.

app-proto/src/main.rs

@@ -5,6 +5,9 @@ mod engine;
 mod outline;
 mod specified;
 
+#[cfg(test)]
+mod tests;
+
 use rustc_hash::FxHashSet;
 use sycamore::prelude::*;
 

app-proto/src/tests.rs

@@ -0,0 +1,14 @@
+use std::process::Command;
+
+// build and bundle the application, reporting success if there are no errors or
+// warnings. to see this test fail while others succeed, try moving `index.html`
+// or one of the assets that it links to
+#[test]
+fn trunk_build_test() {
+    let build_status = Command::new("trunk")
+        .arg("build")
+        .env("RUSTFLAGS", "-D warnings")
+        .status()
+        .expect("Call to Trunk failed");
+    assert!(build_status.success());
+}