Adds a transparent S-expression relay (examples/rpc-relay.lsp) plus a
sequential load generator (examples/rpc-chain-bench.lsp) and a bench
script (tests/rpc-chain-bench.sh) that wires them into multi-hop
chains across runtimes.
The relay is pure byte-forwarding: tcp-accept, tcp-recv, tcp-connect
to backend, tcp-send, tcp-recv reply, tcp-send back. Never parses.
Which is the point — S-expressions are the envelope.
Same rpc-relay.lsp runs as relay in any impl; chains are arbitrary
combinations of {Py, C, asm} nodes.
Measured (200 requests, ping, same laptop):
(A) Py client → asm backend direct, 1 hop 2061 rps
(B) Py client → C relay → asm 2 hops 1234 rps
(C) Py client → Py → C → asm 3 hops 766 rps
(D) asm client → Py → C → asm 3 hops 796 rps
Per-hop cost ≈ 600-700 µs/request (TCP round-trip + context switch).
Safety: every server spawn used the six-layer pattern from CLAUDE.md
(ulimit -v 512MB + timeout 30 + trap + explicit kill + pgrep verify).
Four benchmark cells × up to 3 servers each = 10+ server spawns.
Zero strays, zero safety-net activations.
