Encirclement does not work on map edges

**Describe the bug**
So far I am aware of this strategy/feature "encirclement": if player A's land fully surrounds player B's land (NPC or not), then player B instantly loses and the land becomes owned by player A.

However, this does not work on map edges.

**To Reproduce**
Steps to reproduce the behavior:

1. Start near map edge (Player A)
2. Find a player that is at the map edge (Player B)
3. Surround Player B
4. No encirclement is triggered

**Expected behavior**
Encirclement should occur and Player B loses.

**Screenshots**
(Not screenshot, but an illustration of the situation.)

Consider this hypothetical scenario, where the colors are:
- White: unowned/neutral
- Red: Player A
- Blue: Player B
- Black: out-of-bounds area / map edge

Then, Player A should have encircled Player B, and Player B should lose.

**Desktop (please complete the following information):**

- OS: Windows
- Browser: Firefox
- Version 152

**Additional context**

It may be a good idea to also check lake-side / ocean-side encirclement, to ensure encirclement still works as expected.

**Assignment**

- [ ] I'd like to be assigned to this issue and work on it myself

Comienza reproduciendo el escenario del borde del mapa descrito en el issue y, después, compáralo con un cerco junto a un lago o al océano. Sigue la comprobación del cerco desde el punto de entrada del gameplay; se considerará terminado cuando un jugador completamente rodeado en el borde del mapa pierda y cambie la propiedad, mientras el comportamiento existente fuera del borde siga siendo correcto.

Escrito por el modelo de indexación a partir del texto del issue.