Removed legacy interfaces and old documentation references to the previous on-disk layout

docs/stages/prepare.md

@@ -56,7 +56,7 @@ When `inputs.audio_s3.prefix` is configured, `prepare`:
 4. downloads selected objects to spool audio:
    - `{spool.root}/{campaign}/{session_id}/{run_id}/audio/`
 5. materializes audio into workdir audio:
-   - `{workspace.root}/work/{campaign}/{session_id}/{run_id}/audio/`
+   - `{workspace.root}/work/{campaign}/{session_id}/runs/{run_id}/audio/`
 6. records input provenance in the manifest (bucket, key, metadata, local paths, checksum)
 
 Notes: