Prevent paste pull cursor gaps

[guiyanakuang]

Summary

• centralize persisted and in-memory paste pull cursor updates in a device-scoped manager
• stop remote paste batch processing after the first failed release so a later discard cannot advance past unprocessed data
• serialize device removal with discard cursor persistence and restore the cursor from stored paste data
• make pull-all logging reflect the actual result

Testing

• ./gradlew ktlintFormat
• 36 focused desktop tests covering cursor management, paste pulling, device removal, remote discard, and push behavior