Validate schemas without relying on source filenames

docs/formats.md

@@ -421,6 +421,8 @@ Schemas are JSON documents selected by a prompt or request `schema_path`.
 Directory and `fs.FS` schema paths resolve within the configured root. Each
 schema must be self-contained: in-document references, IDs, and anchors are
 supported, but references requiring another file or network resource fail.
+References must also work without the source filename as a base; use fragment
+references or explicit schema IDs rather than relying on that filename.
 `WithSchemaFile` exposes one schema under its base name. An unreadable,
 invalid, or unresolvable schema causes an operational validation error.
 Valid JSON that fails the schema instead yields a failed validation result.