- B1: Fix --sort-index 0 silent drop by using cmd.Flags().Changed()
instead of value comparison in create-custom and update-custom
- W1: Add MarkFlagRequired("shortcut-id") in remove-custom and
update-custom for consistent error messages
- W2: Extend SYSTEM_BUSY error handling to all write commands
(add/hide/create-custom/remove-custom/update-custom)
- W3: Add duplicate key detection in parseExtension to prevent
silent data loss on repeated --extension keys