Reuse valid workspace checkpoints on request

docs/internal/pipeline.md

@@ -77,6 +77,12 @@ through `pipeline.RunInput`. The runner records source, chunk, extract, merge,
 and normalize outcomes through that interface. Concrete modules do not receive
 workspace paths and do not write checkpoint files directly.
 
+For `run --resume`, the CLI also passes a checkpoint loader. The runner consults
+the loader in workflow order and reuses only checkpoints whose manifest schema,
+status, identity digest, dependency fingerprints, payload files, and payload
+digests validate for the current invocation. Missing or invalid checkpoints fall
+back to normal execution and are refreshed by the recorder.
+
 ## Registries And Module Specs
 
 `pipeline.Registries` holds concrete constructors for execution. A