feat(test): add fallback test crate for no-metadata buildsHEADmain

Add `might_be_async_test_fallback` crate in `test/no_metadata/` to
verify macro behavior when the `metadata_async` feature is absent,
covering sync/async select, invoke, and bare func attributes

1 files changed, 2 insertions, 0 deletions

diff --git a/test/no_metadata/src/lib.rs b/test/no_metadata/src/lib.rs
new file mode 100644
index 0000000..abe379d
--- /dev/null
+++ b/test/no_metadata/src/lib.rs
@@ -0,0 +1,2 @@
+#![allow(unused)]
+include!("../../src/test_fallback.rs");