fix(cliproxy): handle `responses/compact` auth cooldowns and fallback semantics

- Add compact-specific error classification to mark transient/non-credential failures as availability-neutral instead of triggering cooldown penalties.
- Stop auth fallback immediately on compact request-fault errors (e.g., bad/not-found/unsupported request errors) and return the upstream compact error.
- Preserve existing cooldown behavior for auth/credential faults (`401`, `403`, `429`) while allowing non-auth compact failures to fail fast without tainting normal traffic routing.

Closes: #5031