- Add auth_headers/base_url passthrough so RNP and other clients can override
the default Comfy auth + base URL on a per-request basis without a node_cls.
- Add _parse_retry_after helper that honors RFC 7231 Retry-After (seconds or
HTTP-date), feeding the existing 429 / SERVER_BUSY / MAINTENANCE backoff.
- Add rate_limit_label callback so callers can render a friendlier per-second
status (e.g. 'Server busy, retrying in 30s...') during a rate-limit sleep;
the in-flight monitor task is paused so the two writers don't race.
- Add error_parser callback so structured protocol errors (e.g. RNP
RnpProtocolError) bubble unchanged instead of being flattened by
_friendly_http_message; typed errors are also re-raised from poll_op_raw.
- Add allow_304 path returning None on conditional GETs.
- Allow node_cls=None for non-workflow callers; _display_text becomes a no-op.
- _diagnose_connectivity / ApiServerError respect the resolved base_url.
Amp-Thread-ID: https://ampcode.com/threads/T-019e1889-d8bd-732f-8170-b85fd94da503
Co-authored-by: Amp <amp@ampcode.com>
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