Guard updateStateFromHeaders emission with value-change detection to
avoid unnecessary computeAggregatedUtilization scans on every proxied
response. Replace statusAggregateStateLocked two-value return with
comparable statusSnapshot struct. Define statusPayload type for the
status wire format, replacing anonymous structs and map literals.
The usage API itself has rate limits. A 429 from it means "poll less
frequently", not that the account exceeded its usage quota. Previously
incrementPollFailures() was called, marking the credential unusable and
interrupting in-flight connections.
Now: parse Retry-After, store as usageAPIRetryDelay, and retry after
that delay. The credential stays usable and relies on passive header
updates for usage data in the meantime.
