chore: add patch changeset for unknown introspection types

Author: deepanshupal

.changeset/introspect_unknown_type.md

@@ -0,0 +1,7 @@
+---
+default: patch
+---
+
+# Report unknown types during introspection
+
+The `introspect` tool now returns an error with the requested type name when that type is not in the schema, instead of returning an empty successful result. Type names remain case-sensitive.