Fixes a bug where the refresh token was not persisted when the API key
mint failed (e.g., 402 insufficient credits, timeout). The rotated
refresh token was lost, causing subsequent auth attempts to fail with
a stale token.
Changes:
- Persist auth state immediately after each successful token refresh,
before attempting the mint
- Use latest in-memory refresh token on mint-retry paths (was using
the stale original)
- Atomic durable writes for auth.json (temp file + fsync + replace)
- Opt-in OAuth trace logging (HERMES_OAUTH_TRACE=1, fingerprint-only)
- 3 regression tests covering refresh+402, refresh+timeout, and
invalid-token retry behavior
Author: Robin Fernandes <rewbs>
db58cfb13d