Implement final changes from the code quality and deduplication opportunity audit

docs/internal/adapters.md

@@ -14,9 +14,6 @@ Primary adapters:
 - `storage.ObjectStore`
 - `notify.Sender`
 
-Legacy compatibility boundary:
-- `storage.Backend` remains in the storage adapter package and defaults to `NoopBackend`; current pipeline stages use `storage.ObjectStore`.
-
 ## Ownership
 Adapters own:
 - HTTP/subprocess/SDK argument and transport details.

docs/internal/storage.md

@@ -29,9 +29,6 @@ S3 constructor behavior:
 - `Upload` streams local file and returns remote metadata.
 - `Exists` maps not-found responses to `false`.
 
-## Legacy Compatibility Interface
-`storage.Backend` (with `ArchiveRequest`) remains as compatibility surface with `NoopBackend`; it is not used by current stage execution.
-
 ## Invariants
 - storage layer is stateless regarding manifest/stage progression.
 - publish ordering semantics are owned by stage/app code, not storage adapters.

docs/internal/workspace.md

@@ -40,7 +40,7 @@ Run-local outputs are materialized back into canonical session paths before stag
 `artifacts.LocalStore` enforces single-writer session lock via `.lock` file (`ErrLockConflict` on contention).
 
 ## Cleanup Semantics
-Automatic post-publish cleanup (`runPostArchiveCleanup`):
+Automatic post-publish cleanup:
 - only runs when publish actually executed and succeeded;
 - requires `uploaded=true` and `current_pointer_written=true` metadata;
 - respects `pipeline.spool.delete_audio_after_publish` and `pipeline.workspace.cleanup_after_publish`;