fix: stabilize Telegram draft boundaries and suppress NO_REPLY lead leaks (#33169)

* fix: stabilize telegram draft stream message boundaries

* fix: suppress NO_REPLY lead-fragment leaks

* fix: keep underscore guard for non-NO_REPLY prefixes

* fix: skip assistant-start rotation only after real lane rotation

* fix: preserve finalized state when pre-rotation does not force

* fix: reset finalized preview state on message-start boundary

* fix: document Telegram draft boundary + NO_REPLY reliability updates (#33169) (thanks @obviyus)

src/auto-reply/reply/agent-runner.runreplyagent.e2e.test.ts

@@ -410,7 +410,7 @@ describe("runReplyAgent typing (heartbeat)", () => {
         shouldType: false,
       },
       {
-        partials: ["NO_", "NO_RE", "NO_REPLY"],
+        partials: ["NO", "NO_", "NO_RE", "NO_REPLY"],
         finalText: "NO_REPLY",
         expectedForwarded: [] as string[],
         shouldType: false,