0.5.1

Fixed

• Retries: retry_on_statuses is now honored for 5xx responses. Previously any
  status ≥ 500 was coerced into an error and retried unconditionally, ignoring the
  configured status list. 5xx and non-5xx are now governed by the same rule.
• Retries: non-retryable failures (internal, body_too_large, policy_violation,
  circuit_open, canceled, read_error) are no longer retried — they previously
  looped until max_retries was exhausted with no chance of a different outcome.
• Upstream errors: response body and headers of 5xx responses are no longer
  discarded. They are now read and preserved on the upstream response, so error
  detail is available to logging and downstream handling.

Added

• Retries: idempotency guard. Status-based retries now apply only to idempotent
  methods (GET, HEAD, OPTIONS, TRACE, PUT, DELETE). Non-idempotent requests (e.g. POST, PATCH)
  are no longer replayed on a retryable status, preventing duplicate side effects.
  Transport-failure retries are unaffected.

Changed

• Retries: retry decision logic consolidated into a single explicit rule.
  Transport-level failures (timeout, connection) are always retryable;
  status-based retries are driven solely by retry_on_statuses; everything else
  is terminal.
• Used goccy/go-json instead of stdlib encoding/json