Complete compatibility purge audit

docs/internal/artifacts.md

@@ -140,7 +140,8 @@ Extraction sources (`narratio.extraction.*`):
 
 Previous-session sources (`narratio.previous_session.artifact.*`):
 
-- resolve only from local `previous/` cache state;
+- resolve only from one matching `previous_artifact` input record in the
+  current manifest, including its exact source ID and checksum;
 - are hydrated only from the unique `published_output` declaration for their
   canonical source in the selected remote commit; and
 - never infer a path from a previous manifest, current configuration, basename,
@@ -202,10 +203,9 @@ Core helpers:
 - `ValidateCurrentStateIdentity`
 - `RemoteCommitManifest` and `CurrentCommitPointer`
 
-Typed missing-state errors:
+Typed missing-state error:
 
-- `CurrentRunPointerMissingError` (`ErrCurrentRunPointerMissing`)
-- `CurrentManifestMissingError` (`ErrCurrentManifestMissing`)
+- `CurrentCommitPointerMissingError` (`ErrCurrentCommitPointerMissing`)
 
 Identity validation supports caller-provided expectations:
 
@@ -262,7 +262,6 @@ physical layout.
   `internal/artifacts/prepared_input.go`
 - Current state: `internal/artifacts/current_state.go`,
   `internal/artifacts/current_state_commit.go`,
-  `internal/artifacts/current_state_legacy.go`
 - Paths and keys: `internal/artifacts/paths.go`,
   `internal/artifacts/s3_keys.go`
 - Previous requirements: `internal/artifacts/previous_requirements.go`