feat(datasources): publish durable artifact outputs

README.md

@@ -22,8 +22,11 @@ explicit frozen states, previews, retirement, and atomic producer publication.
 Origin discovery retains each provider's source mode, structured health, and
 declared pushdown support. Live previews preserve the provider's effective row,
 serialized-byte, and elapsed-time limits and its redacted diagnostics.
-Producer modules can append a bounded tabular result or create a new static
-datasource through an idempotent capability. The publication ledger retains the
+Producer modules can append a bounded inline tabular result or pin a larger
+durable artifact through the same idempotent capability. Artifact references
+declare a backend, locator, SHA-256 checksum, schema, fingerprint, row and byte
+counts; the installed provider verifies integrity and serves bounded reads.
+The publication ledger retains the
 producer run, output materialization, provenance, and replay identity. On
 PostgreSQL, a transaction-scoped advisory lock serializes each tenant, producer,
 and idempotency identity before any output side effect, so retries from multiple
@@ -37,8 +40,9 @@ materialization provenance. The supported contract is documented in
 
 The contracts already model database, HTTP/REST, directory, file, feed,
 document, binary, directory, and stream sources so providers can be added
-without changing consumers. Larger durable artifact-backed publications remain
-a later storage-provider slice.
+without changing consumers. Storage modules contribute artifact backends
+through the provider-neutral `datasources.artifactBackends` capability; the
+Datasources module never imports their internals.
 
 See [docs/CONCEPT.md](docs/CONCEPT.md) for ownership and lifecycle details.