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/lane-delivery.ts

@@ -8,6 +8,7 @@ export type DraftLaneState = {
   stream: TelegramDraftStream | undefined;
   lastPartialText: string;
   hasStreamedMessage: boolean;
+  previewRevisionBaseline: number;
 };
 
 export type ArchivedPreview = {
@@ -328,6 +329,43 @@ export function createLaneTextDeliverer(params: CreateLaneTextDelivererParams) {
       !hasMedia && text.length > 0 && text.length <= params.draftMaxChars && !payload.isError;
 
     if (infoKind === "final") {
+      const hasPreviewButtons = Boolean(previewButtons?.some((row) => row.length > 0));
+      const canFinalizeDraftPreviewDirectly =
+        isDraftPreviewLane(lane) &&
+        lane.hasStreamedMessage &&
+        canEditViaPreview &&
+        !hasPreviewButtons;
+      let draftPreviewStopped = false;
+      if (canFinalizeDraftPreviewDirectly) {
+        const previewRevisionBeforeFlush = lane.stream?.previewRevision?.() ?? 0;
+        const finalTextSnapshot = text.trimEnd();
+        const hasEmittedPreviewInCurrentLane =
+          previewRevisionBeforeFlush > lane.previewRevisionBaseline;
+        const deliveredPreviewTextBeforeFinal = lane.stream?.lastDeliveredText?.() ?? "";
+        const finalTextAlreadyDelivered =
+          deliveredPreviewTextBeforeFinal === finalTextSnapshot && hasEmittedPreviewInCurrentLane;
+        const unchangedFinalText = text === lane.lastPartialText;
+        lane.stream?.update(text);
+        await params.flushDraftLane(lane);
+        await params.stopDraftLane(lane);
+        draftPreviewStopped = true;
+        const previewUpdated = (lane.stream?.previewRevision?.() ?? 0) > previewRevisionBeforeFlush;
+        const deliveredPreviewTextAfterFinal =
+          lane.stream?.lastDeliveredText?.() ?? deliveredPreviewTextBeforeFinal;
+        if (
+          (previewUpdated && deliveredPreviewTextAfterFinal === finalTextSnapshot) ||
+          (unchangedFinalText && finalTextAlreadyDelivered)
+        ) {
+          lane.lastPartialText = text;
+          params.finalizedPreviewByLane[laneName] = true;
+          params.markDelivered();
+          return "preview-finalized";
+        }
+        params.log(
+          `telegram: ${laneName} draft final text not emitted; falling back to standard send`,
+        );
+      }
+
       if (laneName === "answer") {
         const archivedResult = await consumeArchivedAnswerPreviewForFinal({
           lane,
@@ -340,7 +378,7 @@ export function createLaneTextDeliverer(params: CreateLaneTextDelivererParams) {
           return archivedResult;
         }
       }
-      if (canEditViaPreview && !params.finalizedPreviewByLane[laneName]) {
+      if (canEditViaPreview && !params.finalizedPreviewByLane[laneName] && !draftPreviewStopped) {
         await params.flushDraftLane(lane);
         if (laneName === "answer") {
           const archivedResultAfterFlush = await consumeArchivedAnswerPreviewForFinal({
@@ -372,7 +410,9 @@ export function createLaneTextDeliverer(params: CreateLaneTextDelivererParams) {
           `telegram: preview final too long for edit (${text.length} > ${params.draftMaxChars}); falling back to standard send`,
         );
       }
-      await params.stopDraftLane(lane);
+      if (!draftPreviewStopped) {
+        await params.stopDraftLane(lane);
+      }
       const delivered = await params.sendPayload(params.applyTextToPayload(payload, text));
       return delivered ? "sent" : "skipped";
     }