TASK: Add arrangement_name field to PlaylistItem.Presentation proto message

COMPLETED SUCCESSFULLY

File Modified: php/proto/playlist.proto
Location: PlaylistItem.Presentation message (lines 89-95)

Change Made:
  Added: string arrangement_name = 5;
  After: .rv.data.MusicKeyScale user_music_key = 4;
  Before: closing brace of message

Proto Definition (after change):
  message Presentation {
    .rv.data.URL document_path = 1;
    .rv.data.UUID arrangement = 2;
    .rv.data.Action.ContentDestination content_destination = 3;
    .rv.data.MusicKeyScale user_music_key = 4;
    string arrangement_name = 5;
  }

Field Details:
  - Field number: 5 (correct, sequential after field 4)
  - Field type: string (proto3 syntax)
  - Field name: arrangement_name
  - Purpose: Store arrangement names ("normal", "bene", "test2", etc.)
  - Source: Reverse-engineered from 4 real .proplaylist files

Regeneration Command:
  protoc --php_out=php/generated --proto_path=php/proto php/proto/*.proto

Status: FIELD ADDED AND VERIFIED
