Storage safe-pack verification update

Verified the pack guard and debug no-save toggle.

Safety flow:
1. Extract barrel contents to temporary storage.
2. Check whether the source barrel actually had items.
3. If the source had items but temporary storage is empty, block packing and do not tear down the tent.
4. Commit temporary storage to the tent ID only after the read is safe.
5. Verify the tent-ID saved storage before scheduling teardown.

Debug test:
/function atent:debug/barrel_no_save_on
/function atent:debug/barrel_no_save_off
/function atent:debug/barrel_no_save_status

When the debug toggle is ON, extraction intentionally clears the captured temporary barrel storage. With items in the barrel, the safety guard should block packing before teardown. Empty barrels are also blocked while debug is ON so the test state cannot accidentally pack tents.

Correction made during verification:
The small-tent source-items check was looking at Y - 1, while small save/restore uses Y + 0. This was corrected so small, medium, and large source checks now match their save/restore positions.
