fix(telegram): prevent duplicate messages in DM draft streaming mode (#32118)

* fix(telegram): prevent duplicate messages in DM draft streaming mode

When using sendMessageDraft for DM streaming (streaming: 'partial'),
the draft bubble auto-converts to the final message. The code was
incorrectly falling through to sendPayload() after the draft was
finalized, causing a duplicate message.

This fix checks if we're in draft preview mode with hasStreamedMessage
and skips the sendPayload call, returning "preview-finalized" directly.

Key changes:
- Use hasStreamedMessage flag instead of previewRevision comparison
- Avoids double stopDraftLane calls by returning early
- Prevents duplicate messages when final text equals last streamed text

Root cause: In lane-delivery.ts, the final message handling logic
did not properly handle the DM draft flow where sendMessageDraft
creates a transient bubble that doesn't need a separate final send.

* fix(telegram): harden DM draft finalization path

* fix(telegram): require emitted draft preview for unchanged finals

* fix(telegram): require final draft text emission before finalize

* fix: update changelog for telegram draft finalization (#32118) (thanks @OpenCils)

---------

Co-authored-by: Ayaan Zaidi <zaidi@uplause.io>

src/telegram/draft-stream.ts

@@ -59,6 +59,7 @@ export type TelegramDraftStream = {
   messageId: () => number | undefined;
   previewMode?: () => "message" | "draft";
   previewRevision?: () => number;
+  lastDeliveredText?: () => string;
   clear: () => Promise<void>;
   stop: () => Promise<void>;
   /** Reset internal state so the next update creates a new message instead of editing. */
@@ -127,6 +128,7 @@ export function createTelegramDraftStream(params: {
   let streamDraftId = usesDraftTransport ? allocateTelegramDraftId() : undefined;
   let previewTransport: "message" | "draft" = usesDraftTransport ? "draft" : "message";
   let lastSentText = "";
+  let lastDeliveredText = "";
   let lastSentParseMode: "HTML" | undefined;
   let previewRevision = 0;
   let generation = 0;
@@ -289,6 +291,7 @@ export function createTelegramDraftStream(params: {
       }
       if (sent) {
         previewRevision += 1;
+        lastDeliveredText = trimmed;
       }
       return sent;
     } catch (err) {
@@ -340,6 +343,7 @@ export function createTelegramDraftStream(params: {
     messageId: () => streamMessageId,
     previewMode: () => previewTransport,
     previewRevision: () => previewRevision,
+    lastDeliveredText: () => lastDeliveredText,
     clear,
     stop,
     forceNewMessage,