fix(webhook): remove unused payload from retained delivery state (#2861 salvage)

[hashbender]

Summary

Retained webhook delivery state no longer holds the full request payload — _delivery_info entries kept up to ~1MB of dead weight per delivery for the 1-hour idempotency TTL, and no consumer ever read it (all readers access only deliver / deliver_extra).

Salvage of NousResearch#2861 by @VolodymyrBg (stale branch, cherry-picked onto current main with authorship preserved).

Changes

• gateway/platforms/webhook.py: drop "payload": payload from the retained agent-mode deliver_config (the request-scoped deliver-only dict is untouched)
• tests/gateway/test_webhook_adapter.py: remove the matching fixture key
• scripts/release.py: AUTHOR_MAP entry for @VolodymyrBg

Validation

	Before	After
tests/gateway/test_webhook_adapter.py	—	all pass
payload retained per delivery	up to ~1MB × 1h TTL	none

Infographic

Nous Research

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Mirror-of: NousResearch#56945
NousResearch#56945