A caller's MCP client caps a blocking bridge_send at ~60s, but a real delegated
task runs for minutes. sendAsync runs the same blocking send on a background
virtual thread and returns a ticket; poll(ticket) reports pending/done/failed.
Async reuses the blocking path (and its per-target serialization), so it inherits
reply + completion resolution for free. Surfaces: REST POST message wait:false ->
202 {ticket} + GET /tasks/{ticket}; MCP bridge_send wait flag + new bridge_poll.
Terminal tickets are pruned after a TTL so the registry stays bounded.
Dai Ha
8ed2370fbe