xfail(reify): RecvResult/TryResult channel result types over reify

REIFY Phase 3.0. Add examples/0617 using RecvResult(i64) / TryResult(i64)
(construct + match, plus payload-less .closed / .empty). Seed an empty
expected/*.exit marker. RED by design — the type-fns aren't defined yet
("unresolved RecvResult"); Phase 3.1 adds them to meta.sx as type-fns
over reify and turns this green.

examples/0617-comptime-reify-recvresult.sx

@@ -0,0 +1,37 @@
+// REIFY Phase 3: RecvResult($T) / TryResult($T) — the channel result types,
+// built ENTIRELY in sx library code as type-fns over `reify` (no new compiler
+// machinery beyond Phases 0–1). A blocking recv yields a value or a `closed`
+// marker; a non-blocking try-recv adds `empty` — three states a bool can't
+// express. This locks that they construct and match like any enum, and that
+// `RecvResult(i64)` is one nominal type across sites (the type-fn identity path).
+#import "modules/std.sx";
+#import "modules/std/meta.sx";
+
+main :: () -> i32 {
+    r := RecvResult(i64).value(42);
+    if r == {
+        case .value:  (v) { print("recv value {}\n", v); }
+        case .closed: { print("recv closed\n"); }
+    }
+
+    rc : RecvResult(i64) = .closed;
+    if rc == {
+        case .value:  (v) { print("recv value {}\n", v); }
+        case .closed: { print("recv closed\n"); }
+    }
+
+    t := TryResult(i64).value(7);
+    if t == {
+        case .value:  (v) { print("try value {}\n", v); }
+        case .empty:  { print("try empty\n"); }
+        case .closed: { print("try closed\n"); }
+    }
+
+    te : TryResult(i64) = .empty;
+    if te == {
+        case .value:  (v) { print("try value {}\n", v); }
+        case .empty:  { print("try empty\n"); }
+        case .closed: { print("try closed\n"); }
+    }
+    return 0;
+}