Fix copper golem container transaction logging

[CheekyNox]

Summary

• Capture the selected container through Paper's ItemTransportingEntityValidateTargetEvent.
• Keep the Paper-specific target listener separate from the generic game-event fallback.
• Preserve the first container snapshot across repeated target-validation events.
• Finalize a pending delta before the golem switches between source and destination containers.
• Watch the final interaction so the last 16-item transfer is not lost.

Problem

Copper golems transfer items in batches of 16. Repeated target validation and rapid source/destination switching could replace a pending snapshot before it was logged. This caused missing removals, missing additions, and incomplete totals such as 48 removed or 32 added for a completed 64-item transfer.

Verification

• Tested pickup and deposit transactions on Paper 26.1.2.
• A completed 64-item transfer produces four removed x16 and four added x16 records.
• gradlew build passes.