Recommendation

Wargame Engine is the best-fit rendering layer. Its node-tree viewport, scene system, messaging architecture, and board wargame domain align with the LangGraph graph model at an architectural level, not just a metaphorical one. The engine is small (52 commits), Python/pygame, pip-installable, and maintained as of 2024. It runs on any platform pygame supports (including ARM Linux on RG40XXV).

Fallback: If Wargame Engine proves too opinionated (owns the game loop, resists LangGraph’s invoke-driven state model), fall back to raw pygame or Python Arcade. The cost is having to rebuild the node-tree viewport, scene management, and GUI system from scratch — but the prototype scope (10 units, turn-based) makes this tractable.

Sequtus is worth a skim for its Pygame RTS patterns (selection, orders, minimap) but not as a foundation.