Chain arcs now follow real surfaces as targets move

In Shattered Rift, moving chain arcs now follow real surface endpoints instead of leaving world-fixed rectangles. A same-frame defect let a second chain hit an already-dead enemy; queued targets are now skipped, with damage and order on surviving targets preserved. Mining reward streams keep their full length and follow the belly through motion and fade. The player-camera clips use a controlled three-enemy corridor and one relocated deposit as test setup. They are offline 1080p60 output, not sustained 60 FPS on hardware. The explosion sphere and bloom, close combat, art, loading and performance remain open.