Implemented new campaign/session stable inputs and corresponding input source references

docs/internal/stage-prepare.md

@@ -5,7 +5,7 @@ Materialize canonical current-session inputs before processing stages.
 
 ## Inputs
 - resolved `campaign.yml`, `session.yml`, and pipeline config
-- stable input files (`speakers`, `autocorrect`, `glossary`)
+- stable input files (`speakers`, `autocorrect`, `glossary`, `players`, `party`)
 - audio source:
   - local `audio_dir`/`audio_files`, or
   - S3 `audio_s3.prefix`
@@ -18,6 +18,8 @@ Materialize canonical current-session inputs before processing stages.
 - `inputs/speakers.yml`
 - `inputs/autocorrect.yml`
 - `inputs/glossary.yml`
+- `inputs/players.yml`
+- `inputs/party.yml`
 - `audio/*.flac`
 - optional `previous/manifest.json`
 - optional `previous/artifacts/**`