Borrows one exclusive egress connection for one or more serial queries.
Borrows an exclusive fluent sender; close() flushes and returns its slot.
Rejects new borrows and closes idle resources. Borrowed query sessions are cancelled and closed; borrowed senders retain ownership during a bounded drain and own their teardown if they outlive it.
Pre-connects the configured minimum sender and query pool sizes.
Browser-safe facade owning bounded ingress and egress connection pools. Borrowed handles are exclusive; separate query leases execute concurrently.