Implement Studio root and placement capabilities on the replica graph (WI-10)

test/portable-bindings.test.ts

@@ -50,7 +50,7 @@ test("generation rejects remote dependencies, wrong effects and unsupported shap
   assert.throws(generate, /not an object call available in portable target browser/);
   getter.execution = { kind: "snapshot", targets: ["browser", "server"] };
   entry.dependencyPorts[0]!.requirement = { kind: "reflection", selectors: ["active"] };
-  assert.throws(generate, /Unsupported reflection port/);
+  assert.throws(generate, /Only checked presentation metadata is portable/);
 });
 
 test("closed generic portable handlers have distinct concrete codecs and no universal casts", async () => {