* fix(zalo): adopt durable ingress drain with ack gated on raw-envelope append
OA webhooks acked before detached processing behind a 5-minute in-memory
guard, and Zalo does not retry (silent loss). Raw webhook JSON now appends
durably (event_id = Bot API message.message_id, lane per chat.id) before the
200; failed appends answer 400/500 so nothing acks unpersisted. Dispatch runs
through the core drain with serialized admissions across append backoff,
deferred claims held through shutdown until adoption, retry/dead-letter
classification, and 30d/20k tombstones replacing the deleted 5min/5k guard
after its parity test. Webhook and polling transports stay mutually
exclusive; no twin scenario exists across the four received-event types.
Autoreview scanner false-positive on deleted-line token field references; full
manual review performed (ack ordering, dual-transport exclusivity, eleven-test
matrix). Part of the #109657 fleet program (wave 3).
* refactor(zalo): keep webhook runtime exports private
* test(zalo): use managed temp directories