macros, vm, bytecode: add #[primop] await-style primop macro

fix-vm/src/macro_support.rs

@@ -0,0 +1,36 @@
+//! Single macro-facing path for the `#[primop]` support surface: the traits
+//! generated code type-checks through (defined in `fix_runtime`, where the
+//! impl sets are coherent) and the stub trio that keeps un-expanded primop
+//! sources resolving in tooling.
+
+use std::future::Future;
+
+pub use fix_runtime::{CalleeReady, ForceTarget, UnwrapSlot};
+use fix_runtime::{Slot, Value};
+
+macro_rules! type_hint {
+    () => {
+        if false {
+            return async {
+                unreachable!();
+            };
+        }
+    };
+}
+
+#[expect(clippy::panic, reason = "deliberately panic when the stub is called")]
+pub fn force<T>(_: Slot<Value<'_>>) -> impl Future<Output = Slot<T>> {
+    type_hint!();
+    panic!("stub `force` called at runtime")
+}
+
+#[expect(clippy::panic, reason = "deliberately panic when the stub is called")]
+pub fn call<T, A, R>(_: &T, _: A) -> impl Future<Output = R> {
+    type_hint!();
+    panic!("stub `call` called at runtime")
+}
+
+#[expect(clippy::panic, reason = "deliberately panic when the stub is called")]
+pub fn spill<T>(_: T) -> Slot<T> {
+    panic!("stub `spill` called at runtime")
+}