docs(aggregator): state the alert throat's truth contract in alerts.ts (#3703)

pm-stack/aggregator/src/alerts.ts

@@ -9,6 +9,17 @@
 // immediately, quiet hours or not, because the sentinels are
 // external to the thing that might be down. Warnings never push in
 // v1 (page + ledger only).
+//
+// The throat's truth contract (#3702 Phase 3, 2026-11-03): the alert
+// throat's records and responses tell the truth and keep its secrets.
+// A state transition is recorded only when the event it names happened
+// (delivered / escalated require at least one accepted send; `gone` is
+// not a send). Subscription key material (`p256dh`, `auth`) never
+// leaves the server: store rows are internal, any HTTP surface
+// projects — the page's projection is the only read shape. Subscription
+// preferences are validated as values, not shapes, and an invalid value
+// falls back per-field to the default — never stored, never
+// reinterpreted.
 import type { Config } from "./config.ts";
 import { sendPush, type PushOutcome, type PushTarget } from "./push.ts";
 import { getSupabaseClient, sqlInt, sqlJson, sqlStr, type SupabaseClient } from "./supabase.ts";