Terrain Tool Expansion - World Compatibility

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### Is your feature request related to a problem? Please describe.

Right now, the terrain tool only works for a single TMX file at a time. It would be cool if when drawing near the borders of a map within a world that it automatically detects the edges of adjacent maps and applies the terrain tool's painting where appropriate.

If a map is also the only in the world, the terrain stamp should detect the opposite edge so that one can easily make looping maps.

### Describe the solution you'd like.

Summary: Instead of clipping at the edge of the map when painting tiles with the Terrain Stamp. It should instead detect the appropriate edge for a TMX file that is adjacent to the one that you are drawing on. I will provide visual cues later.

### Describe alternatives you've considered.

_No response_

Start by tracing the Terrain Stamp painting path and how a world exposes adjacent TMX maps. Check behavior at map borders and for a single map configured to loop; done means terrain painting reaches the appropriate neighboring or opposite edge instead of clipping. The issue notes that visual cues are still to be provided.

Written by the indexing model from the issue text.