Trying to delete a wallmount deletes all of them on that layer

Expected behavior:
- deleting a placed object should only clear the requested direction on that tile
- the clear operation should not wipe every placed object on the same layer
- keep the change limited to the tile-map clearing logic

--- Original GitHub issue (auto-fetched) ---
Title: Trying to delete a wallmount deletes all of them on that layer

Body:
<!-- The notes within these arrows are for you but can be deleted. -->

## Summary

Trying to delete a wallmount deletes all of them on that layer.

## Steps to Reproduce

Lay multiple wallmounts on a single wall tile at different rotations.
Try to delete just one.

## Expected Behavior

Only the direction the hologram is rotated should be deleted.
