* fix: propagate Slack reply errors
Co-authored-by: Johannes du Plessis <51395795+johannes117@users.noreply.github.com>
* fix: classify Slack 429 as rate_limited with retry-after
Slack chat.postMessage rate limiting returns HTTP 429, which raise_for_status
turned into a generic http_error and told the agent to retry immediately,
ignoring Slack's retry window. Special-case 429 (threading Retry-After) and
normalize the ratelimited body code before the generic HTTP path so the
existing rate_limited hint actually fires.
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Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>
Co-authored-by: Johannes du Plessis <51395795+johannes117@users.noreply.github.com>
Co-authored-by: Johannes du Plessis <johannes@langchain.dev>
