The Portal's /api/nous/recommended-models endpoint is the source of truth for
which models are free/paid right now, but its result was cached in-process
only. When the live fetch failed (network, parse, non-2xx), the function
returned {} and the model picker silently dropped the free/paid
recommendations — free models would vanish with no indication anything went
wrong.
Add a per-base disk cache at $HERMES_HOME/cache/nous_recommended_cache.json:
a successful live fetch is persisted as last-known-good, and a failed fetch
with an empty in-process cache falls back to the disk copy instead of {}.
Self-heals on the next successful fetch. With no disk copy, still degrades to
{} (callers already handle that). Keyed by portal base URL so staging/prod
don't collide.
E2E: live fetch writes disk; simulated Portal failure returns the cached free
models from disk; no-disk + failure returns {}.
e687292eb4