Add output validation against a defined JSON schema

README.md

@@ -199,6 +199,14 @@ Segments are sorted deterministically by:
 
 Final segment IDs are assigned after sorting and start at `1`.
 
+The public Go output contract is available from:
+
+```go
+import "gitea.maximumdirect.net/eric/seriatim/schema"
+```
+
+The same package embeds the machine-readable JSON Schema in `schema/output.schema.json`. The default `validate-output` postprocessor validates the output shape and verifies final segment IDs are present, sequential, and start at `1`.
+
 ## Overlap Detection
 
 The default postprocessing pipeline detects overlapping segment groups.