Improve the architecture by configuring the playlist handle directly
in register_playlist() instead of deferring it to run().
Changes:
- Remove playlist_handle_pending field (no longer needed)
- register_playlist() now calls logic_mut() to configure immediately
- run() becomes a simple delegation with no configuration logic
- Follows proper pattern: configuration before run(), not during run()
This is cleaner than the previous approach which used a pending field
and transferred it during run(). The new approach:
1. User calls register_playlist() → directly configures logic
2. User calls run() → simple delegation to inner.run()
Architecture now properly separates configuration from execution.
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