fix(carousel): remove hasSubtitle proto field + add debug logging

- Remove hasSubtitle (field 10) from Header proto definition, index.js
  and index.d.ts - this field was adding extra bytes to encoded protobuf
  that working implementations don't send, potentially causing rejection
- Remove hasSubtitle from carousel card headers and root header
- Add [CAROUSEL DEBUG] logging in relayMessage to dump:
  - Encoded message bytes as base64 (for binary comparison)
  - Message structure as JSON
  - Per-device encoded bytes with DSM flag
- This enables byte-level comparison with working implementations

https://claude.ai/code/session_01EK9NpViRCtda1WAvFd8ptR

WAProto/index.d.ts

@@ -6854,7 +6854,6 @@ export namespace proto {
                 title?: (string|null);
                 subtitle?: (string|null);
                 hasMediaAttachment?: (boolean|null);
-                hasSubtitle?: (boolean|null);
                 documentMessage?: (proto.Message.IDocumentMessage|null);
                 imageMessage?: (proto.Message.IImageMessage|null);
                 jpegThumbnail?: (Uint8Array|null);
@@ -6868,7 +6867,6 @@ export namespace proto {
                 public title?: (string|null);
                 public subtitle?: (string|null);
                 public hasMediaAttachment?: (boolean|null);
-                public hasSubtitle?: (boolean|null);
                 public documentMessage?: (proto.Message.IDocumentMessage|null);
                 public imageMessage?: (proto.Message.IImageMessage|null);
                 public jpegThumbnail?: (Uint8Array|null);