Implementation plan and status

Phases A-D in the README are complete. The RFD remains active for one shared integration gate:

• scoped, borrow-capable tasks with real wakers and join/cancel/drain are tracked as Trait Solving Step 2;
• the quiescence/fallback-finalization body-completion state machine is tracked as Trait Solving Step 11;
• Method Resolution consumes both through retained lookup obligations.

Those checkboxes live in the Trait Solving implementation plan so one landed change has one authoritative per-step status. When that gate lands, complete this RFD's lifecycle update together with the roadmap and architecture pages.