feat: Add playlist management functionality and compliance checks

- Introduced a new "Playlists" column in results view with visual indicators for membership.
- Added `playlist_api.py` to handle playlist-related operations (fetch, add, remove tracks).
- Implemented `PlaylistManagerDialog` for seamless playlist addition/removal with caching.
- Integrated compliance check script (`check_agents_compliance.py`) for ensuring coding standards.
- Added extensive documentation (`playlist_membership_manager.md`) covering architecture and flow.
- Updated GUI logic and QStandardItemModel setup to include playlist data.
- Included unit tests for playlist management components and API.

tidal_dl_ng/helper/playlist_api.py

@@ -0,0 +1,191 @@
+"""Playlist API helper - Centralized API calls for playlist operations.
+
+This module provides a clean interface for all playlist-related API operations,
+abstracting the tidalapi session details and providing consistent error handling.
+
+All functions are synchronous and should be called from worker threads.
+"""
+
+from requests.exceptions import RequestException
+from tidalapi import Session, Track, UserPlaylist
+
+from tidal_dl_ng.logger import logger_gui
+
+
+def get_user_playlists(session: Session) -> list[UserPlaylist]:
+    """Fetch all user playlists from Tidal API.
+
+    Args:
+        session: Authenticated Tidal session
+
+    Returns:
+        List of UserPlaylist objects
+
+    Raises:
+        RequestException: If API call fails
+        ValueError: If user is not authenticated
+    """
+    if not session.user:
+        raise ValueError("User not authenticated")  # noqa: TRY003
+
+    try:
+        playlists = session.user.playlists()
+        return list(playlists) if playlists else []
+    except RequestException as e:
+        logger_gui.error(f"Failed to fetch user playlists: {e}")
+        raise
+
+
+def get_playlist_items(playlist: UserPlaylist) -> list[Track]:
+    """Fetch all items from a playlist.
+
+    Args:
+        playlist: UserPlaylist object
+
+    Returns:
+        List of Track objects in the playlist (excludes videos and other media types)
+
+    Raises:
+        RequestException: If API call fails
+    """
+    try:
+        # Force refresh to get latest items
+        playlist._items = None
+
+        # Replace single-call fetching by robust pagination to retrieve ALL items
+        # Some tidalapi backends return only the first N items (e.g., 100) by default.
+        # We iterate with an offset/limit until exhaustion.
+        all_items: list[Track] = []
+        offset: int = 0
+        limit: int = 100  # Use API-supported page size to avoid 400 errors
+
+        while True:
+            try:
+                batch = playlist.items(offset=offset, limit=limit)
+            except TypeError:
+                batch = playlist.items(offset, limit)
+
+            if not batch:
+                break
+
+            # Filter to only include Track objects
+            tracks_batch = [item for item in batch if isinstance(item, Track)]
+            all_items.extend(tracks_batch)
+
+            # Progress
+            offset += len(batch)
+
+            # Safety: stop if no progress to avoid infinite loop
+            if len(batch) < limit:
+                break
+
+    except RequestException as e:
+        logger_gui.error(f"Failed to fetch playlist items for {playlist.id}: {e}")
+        raise
+    else:
+        # Silenced diagnostics: previously logged first few tracks for ID normalization
+        return all_items
+
+
+def add_track_to_playlist(session: Session, playlist_id: str, track_id: str) -> None:
+    """Add a track to a playlist.
+
+    Args:
+        session: Authenticated Tidal session
+        playlist_id: UUID of the playlist
+        track_id: UUID of the track to add
+
+    Raises:
+        RequestException: If API call fails
+        ValueError: If playlist not found
+    """
+    try:
+        playlist = session.playlist(playlist_id)
+        if not playlist:
+            raise ValueError(f"Playlist {playlist_id} not found")  # noqa: TRY003
+
+        # Normalize ID as int where supported
+        try:
+            norm_id = int(track_id)
+        except (TypeError, ValueError):
+            norm_id = track_id
+
+        playlist.add([norm_id])
+        # Silenced info log
+    except RequestException as e:
+        logger_gui.error(f"Failed to add track {track_id} to playlist {playlist_id}: {e}")
+        raise
+
+
+def remove_track_from_playlist(session: Session, playlist_id: str, track_id: str) -> None:
+    """Remove a track from a playlist.
+
+    Args:
+        session: Authenticated Tidal session
+        playlist_id: UUID of the playlist
+        track_id: UUID of the track to remove
+
+    Raises:
+        RequestException: If API call fails
+        ValueError: If playlist or track not found
+    """
+    try:
+        playlist = session.playlist(playlist_id)
+        if not playlist:
+            raise ValueError(f"Playlist {playlist_id} not found")  # noqa: TRY003
+
+        # Always use index-based removal with robust pagination
+        # Force refresh and paginate to get all items
+        playlist._items = None
+        items_all = []
+        offset = 0
+        limit = 100
+        while True:
+            try:
+                batch = playlist.items(offset=offset, limit=limit)
+            except TypeError:
+                batch = playlist.items(offset, limit)
+            if not batch:
+                break
+            items_all.extend(batch)
+            offset += len(batch)
+            if len(batch) < limit:
+                break
+
+        # Find the track index
+        track_index = None
+        for i, item in enumerate(items_all):
+            item_id = getattr(item, "id", None)
+            if str(item_id) == str(track_id):
+                track_index = i
+                break
+
+        if track_index is None:
+            # Silenced warning: skip quietly if not found
+            return
+
+        # Remove by index
+        playlist.remove_by_index(track_index)
+        # Silenced info log
+    except RequestException as e:
+        logger_gui.error(f"Failed to remove track {track_id} from playlist {playlist_id}: {e}")
+        raise
+
+
+def get_playlist_metadata(playlist: UserPlaylist) -> dict[str, str | int]:
+    """Extract metadata from a playlist object.
+
+    Args:
+        playlist: UserPlaylist object
+
+    Returns:
+        Dictionary containing:
+            - name: Playlist name
+            - item_count: Number of items in playlist
+            - id: Playlist UUID
+    """
+    return {
+        "name": playlist.name if hasattr(playlist, "name") else f"Playlist {playlist.id}",
+        "item_count": playlist.num_tracks if hasattr(playlist, "num_tracks") else 0,
+        "id": str(playlist.id),
+    }