docs consolidation work

docs/modules/notify/operations/retries.md

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+# Retry and idempotency policy (NR5)
+
+- `delivery_id`: UUIDv7; `dedupe_key`: hash(event_id + rule_id + channel_id).
+- Backoff: exponential with jitter; base 2s, factor 2, max 5 attempts, cap 5 minutes between attempts.
+- Connectors must be idempotent; retries reuse the same `dedupe_key` and must not duplicate sends.
+- Out-of-order acks ignored: only monotonic `attempt` accepted.
+- Record retry outcomes in receipts and include attempt count + reason.