Add complete playlist management

[austin-smith]

Summary

Expand playlist support from browsing and appending items into complete management of playlists the signed-in user is allowed to modify.

The user-facing feature set should include:

• Creating a playlist with a name, description, and visibility
• Renaming a playlist and changing its description or visibility
• Adding tracks or episodes at a chosen position, not only at the end
• Removing a selected playlist item
• Reordering playlist items
• Removing or unfollowing a playlist from the user's library

Why

Adding the current item to a playlist is useful, but common playlist work still requires leaving the terminal. Completing the basic edit lifecycle would make playlists a real working surface rather than a mostly read-only destination.

Important behavior

• Only offer mutations when Spotify permits the signed-in user to perform them. Ownership and collaboration capabilities should be explicit; a playlist being public or followed does not imply that it can be edited or even fully enumerated.
• Use Spotify's playlist snapshot identifiers where relevant so a stale screen cannot silently reorder or remove the wrong item after the playlist changes elsewhere.
• Handle duplicate URIs deliberately. Removing one selected occurrence should not unexpectedly remove every copy of that track or episode.
• Ask for confirmation before destructive or broad changes, especially clearing/replacing content or removing a playlist from the library.
• Refresh the shared playlist catalog and any open playlist view after a successful mutation without discarding the user's navigation position.
• Surface permission conflicts, stale snapshots, unavailable items, and rate limits as actionable errors.

Out of scope

• Reordering or removing items from Spotify's playback queue; the Player API does not expose those operations
• Playlist folders, which are not exposed by the Web API
• Automatic or recommendation-generated playlists

References

• Create Playlist
• Change Playlist Details
• Add Items to Playlist
• Remove Playlist Items
• Update Playlist Items
• Save Items to Library
• Remove Items from Library