fix(routing): unify session delivery invariants for duplicate suppression (#33786)

* Routing: unify session delivery invariants

* Routing: address PR review feedback

* Routing: tighten topic and session-scope suppression

* fix(chat): inherit routes for per-account channel-peer sessions

src/agents/pi-embedded-messaging.ts

@@ -5,6 +5,7 @@ export type MessagingToolSend = {
   provider: string;
   accountId?: string;
   to?: string;
+  threadId?: string;
 };
 
 const CORE_MESSAGING_TOOLS = new Set(["sessions_send", "message"]);