Made buildings obstruct power links

I made buildings obstruct power links. A relay can no longer draw a wire straight through a structure just because the endpoints are close enough.

The line-of-sight check ignores mobile units and the two linked endpoints, but checks substantial intervening buildings. Players can route poles around an obstruction while keeping the existing span limits.

“Relay line of sight respects buildings while ignoring mobile units and the linked endpoints.”

The clips inspect an initialized wind generator, relay and wall. The actual placement interface rejects their twelve-metre link with the blocked-building warning; this is a deliberately paused placement inspection.