v0.37.0 — the credential never enters the sandbox

The credential broker is now on by default for every operator (Claude, Codex) on every platform. The model credential stays host-side and is injected on the wire — the untrusted sandbox never sees it. Log into Claude once and never touch a token again (host-side auto-refresh); Codex's curl_cffi TLS helper installs itself with zero user step.

Fixes that only bit native Linux (Docker Desktop had masked them on macOS): the broker reaches the host over the docker bridge gateway, nethackers setup prints the one-time port-scoped ufw rule, and the arena output dir is writable by the sandbox — the last one had been crashing every native-Linux evolve/eval.

Host-side only: no sandbox-image behaviour change, arena re-pinned at the same scoring major (verified leaderboard unaffected).

Verified end-to-end on macOS and a real Linux host — nethackers setup, the live broker round-trip for both operators against this release's sandbox image, and a full evolve pipeline.