normalEmbed removable FIFO

Chose a removable FIFO with at most 64 retained normal-embedding waiters over a promise-tail chain because canceled or unresolved promises can retain ownership and contaminate later work. Do not count the active owner; physically remove canceled waiters and transfer release to the oldest live waiter. Normal and recall work require finite provider deadlines, while single-text recall bypasses only FIFO admission—not execution ownership or cleanup.