[Feature]: Make bounding box not overlap edge of building when placing flooring

Problem / motivation

The amber box currently extends over the edge of the building, when the cursor is positioned fairly close to the edge. It is subtle but probably not the best behavior. When i move the cursor over the edge the entire box turns red which is fine and should be retained. I think this is a mode agnostic issue as it just is about the affordances for construction (ghost cursors).

Proposed solution

I think the amber-yellow box should narrow down along the outward side (in this screenshot the left side) so that it does not extend beyond the building, and the outside edge remains flush to the existing flooring below it.

Alternatives considered

The box could be split between red and amber but I think that looks ugly.

Which game mode should this target?

Both / mode-agnostic

Before submitting

• I searched existing issues and this is not a duplicate.

Start by tracing the flooring placement ghost cursor and reproduce the edge case shown in the issue. The amber bounding box should remain flush with existing flooring and stay within the building edge, while the full red state remains unchanged in both game modes.