ShouldSendWithoutBlockingQUIC: a burst of 256 sends of 64 KiB returns in
a few milliseconds with most of it still in flight by BytesInFlight();
every send then reports true, once, in the order sent, the counters
drain to zero and the peer reads all 16 MiB in order. With every pool
worker parked, a chain of 100 sends, each made from the previous one's
onSent, completes. A connection stopped under a burst reports every send
once, the trues before the falses; sends made just before the wrapper is
destroyed go out and report true; four threads sending on one stream at
once all hear back; and a send on a closed stream reports false from a
pool task rather than from inside SendAsync. Readers on the server are
threads of their own, so parking the pool parks nothing they need.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
