feat(import): include cover-art attachments in --export/--import

Export URL-backed attachments per title and rebuild them on import so they ride along into the muxed output. Local font attachments are skipped (not portable).

unshackle/commands/dl.py

@@ -2829,6 +2829,9 @@ class dl:
                     {"timestamp": chapter.timestamp, "name": chapter.name} for chapter in (title.tracks.chapters or [])
                 ]
 
+            if "attachments" not in tinfo:
+                tinfo["attachments"] = [a.to_dict() for a in (title.tracks.attachments or []) if a.url]
+
             export.write_text(json.dumps(doc, indent=4, ensure_ascii=False), encoding="utf8")
 
     def prepare_drm(

unshackle/core/import_service.py

@@ -18,6 +18,7 @@ from unshackle.core.manifests import DASH, HLS, ISM
 from unshackle.core.remote_service import RemoteService, _build_title, _resolve_proxy
 from unshackle.core.titles import Episode, Movies, Series, Title_T, Titles_T, remap_titles
 from unshackle.core.tracks import Audio, Chapter, Chapters, Tracks, Video
+from unshackle.core.tracks.attachment import Attachment
 from unshackle.core.tracks.track import Track
 
 log = logging.getLogger("import")
@@ -166,6 +167,23 @@ class ImportService:
                     track.drm = drm
                 tracks.add(track)
 
+        for attachment in entry.get("attachments") or []:
+            url = attachment.get("url")
+            if not url:
+                continue
+            try:
+                tracks.attachments.append(
+                    Attachment.from_url(
+                        url,
+                        name=attachment.get("name"),
+                        mime_type=attachment.get("mime_type"),
+                        description=attachment.get("description"),
+                        session=self.session,
+                    )
+                )
+            except Exception as e:
+                self.log.warning(f"Skipping attachment '{attachment.get('name')}': {e}")
+
         self.tracks_by_title[title_id] = tracks
         return tracks
 

unshackle/core/tracks/attachment.py

@@ -125,6 +125,10 @@ class Attachment:
     def __str__(self) -> str:
         return " | ".join(filter(bool, ["ATT", self.name, self.mime_type, self.description]))
 
+    def to_dict(self) -> dict[str, Optional[str]]:
+        """Serialise a URL-backed attachment for export/import."""
+        return {"url": self.url, "name": self.name, "mime_type": self.mime_type, "description": self.description}
+
     @property
     def id(self) -> str:
         """Compute an ID from the attachment data."""