run_worker only polled shutdown.changed() inside the select! arm, which the
claim-and-spawn branch skips via continue whenever there's ready work. Under
a sustained stream of ready claims (a boot sweep across agents is the
realistic case) exit was deferred until the queue happened to drain instead
of being observed promptly.
check *shutdown.borrow() explicitly at the top of every loop iteration
instead of relying solely on the select! arm, so a busy loop still sees
shutdown promptly.
also documented why dropping pending Queued DAGs on shutdown is safe: every
NodeKind is idempotent-convergent, which is a property of the node set, not
of the queue, and isn't enforced by the type system. flagged the side-effect
tails (EmitRebuilt, ResolveApproval) as the ones closest to the edge.
fixeshyperhive/hyperhive#2848
c16c31c0f9