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/bot-message-dispatch.ts

@@ -225,6 +225,7 @@ export const dispatchTelegramMessage = async ({
       stream,
       lastPartialText: "",
       hasStreamedMessage: false,
+      previewRevisionBaseline: stream?.previewRevision?.() ?? 0,
     };
   };
   const lanes: Record<LaneName, DraftLaneState> = {
@@ -259,6 +260,7 @@ export const dispatchTelegramMessage = async ({
   const resetDraftLaneState = (lane: DraftLaneState) => {
     lane.lastPartialText = "";
     lane.hasStreamedMessage = false;
+    lane.previewRevisionBaseline = lane.stream?.previewRevision?.() ?? lane.previewRevisionBaseline;
   };
   const updateDraftFromPartial = (lane: DraftLaneState, text: string | undefined) => {
     const laneStream = lane.stream;