v6.5.3-beta.4

Over v6.5.3-beta.3:

• The stale purge of entities restored from previous versions now also removes their device registry entry. Legacy entities (created before the stable-identity rework) carry unique ids that cannot be mapped back to device identifiers, so beta.3 would have removed the entity but left an empty device shell; the purge now goes through the entity's device id, keeping devices that still have other entities.
• Documentation: options table in the README, worked deny/allow filter examples in the configuration guide, and an architecture section on the February 2026 Spotify API removals, the grandfathered client id behavior, and spotipy's fake-429 quirk.

See v6.5.3-beta.2 for the full feature list.