~x-ai/grok-latest → B (1:4)

B fixes a real production deadlock in `rpc.rs` by scoping `RwLock` read guards so they drop before nested `read`/`write` on RoomCreate/RoomGrant, plus a regression test and server log-pipe deadlock avoidance in `start-server`. A only deduplicates Babashka test helpers (assert/ANSI, cargo build, mock Google, registration flow) with no product correctness impact.