Segment Seat Availability
 [x] No overlap when segments only touch at handoff
 [x] No overlap adjacent legs
 [x] Overlap when inner segment inside outer
 [x] Overlap when longer segment contains shorter
 [x] No overlap when only share drop of first with pick of second
 [x] Unknown stops do not overlap
 [x] Resolve booking segment prefers ticket pick drop
 [x] Parse stoppage trims and filters
 [x] Segments overlap by order matches interval logic

