Render when vehicles are waiting to spawn at a building or border

If a vehicle is trying to exit a building driveway but has no room to spawn, it'll invisibly keep retrying. Same for starting at a border intersection. We should visually represent that something's there waiting, at least.

Look for code handling vehicle spawning from buildings and borders, likely in a simulation or vehicle module. Identify where spawn retries happen and add a visual indicator (like an icon or highlight) to the map rendering system. Check existing UI components for similar status displays to understand the graphics pipeline.

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