newLoomPair

Provide a fresh host/joiner Loom pair per test.

• .first hosts via host(pattern) (weave(Rendezvous.New(pattern)))

• .second joins via join(joinTag()) (weave(Rendezvous.Existing(joinTag()))) In-process radio fabrics return the SAME instance twice: (loom, loom). Role-split fabrics return DISTINCT host/joiner Looms wired to reach each other.