Integrate and tune the Repulsor (pathfinder)

[onlycs]

I have a copy of RepulsorFieldPlanner.java from 1155 and last year's Navigate API integrated, will make a PR when I get home today.

Will need tuning and updates for the 2026 field (obstacles).

[onlycs]

see

4b077a5

and

1bdc1df

on branch old-master. should have most, if not all the code I plan to add.