Download S3 audio during prepare

docs/roadmap/narratio-s3-archive-implementation-plan.md

@@ -103,7 +103,6 @@ Implemented in repository:
 
 Not implemented yet:
 
-- prepare-stage S3 list/download behavior
 - archive-stage S3 upload behavior
 - promotion uploads
 - writing `current/manifest.json` and `current/run_id.txt` to S3
@@ -314,7 +313,7 @@ work/audio
 transcribe
 ```
 
-The `prepare` stage should:
+Implemented `prepare` behavior:
 
 1. list `.flac` objects under the configured S3 audio prefix,
 2. fail clearly if none are found,
@@ -331,7 +330,11 @@ spool:
   delete_audio_after_archive: true
 ```
 
-For v1, prefer retaining local workdir audio until the run has successfully archived. The source of truth remains S3, but local diagnostics are valuable during development.
+Current boundary:
+
+- downloaded audio is retained in spool/workdir
+- spool cleanup policy remains future work
+- archive does not upload source audio by default
 
 ## 6. Configuration Design