feat(import): add deterministic OpenAPI normalized IR

crates/crank-import/tests/fixtures/openapi-3.1.json

@@ -0,0 +1,9 @@
+{
+  "openapi": "3.1.0",
+  "info": { "title": "Fixture OpenAPI 3.1" },
+  "paths": {
+    "/health": {
+      "get": { "responses": { "200": { "description": "OK" } } }
+    }
+  }
+}