Support explicitly reference-selected read-only interface dependencies

src/capability-model/validation.ts

@@ -1418,6 +1418,15 @@ const validateBoundDependencies = (
       }
       case "interface": {
         const interfaceBinding = binding as Extract<DependencyBinding, { kind: "interface" }>;
+        if (interfaceBinding.receiver !== requirement.receiver || (interfaceBinding.receiver && interfaceBinding.via)) {
+          issue(
+            issues,
+            "invalid-dependency-binding",
+            path,
+            "Reference-selected interface ports require an explicit matching from input binding",
+          );
+          break;
+        }
         if (interfaceBinding.interfaceRevisionId !== requirement.interfaceRevisionId) {
           issue(
             issues,
@@ -1427,6 +1436,9 @@ const validateBoundDependencies = (
           );
           break;
         }
+        // The reference supplies its own checked witness at invocation time.
+        // This is not a requirement that the current receiver implements the interface.
+        if (interfaceBinding.receiver === "input") break;
         const traversal = interfaceBinding.via
           ? validateTraversal(
               issues,