Archive session management plugin

Key features

• Archived Sessions settings page — placed directly after Connectors and grouped by workspace.
• A deleted session is removed from its transcript directory, workspace records, archived-session set, and projection cache.
• Dark session cards — show the session title and update time with explicit restore and delete actions.
• Safe unarchive — restores a session to its original workspace position.
• Permanent deletion — removes the transcript, workspace accounting, archive marker, and projection-cache record after confirmation.