Selecting nothingness

To make deleting tiles easier, it would be nice if you could select nothingness by right clicking, just like other tiles can be selected, and then click to replace tiles with the selected nothingness, essentially deleting the replaced tiles.
This would be easier and faster than changing to the eraser and back, even with keyboard shortcuts.

No files or tests are named. Start by tracing the editor's tile-selection and eraser workflows, then determine where right-click selection and tile replacement are handled. Done means right-clicking can select nothingness and clicking replaces the targeted tiles without switching tools.

Written by the indexing model from the issue text.