fix(telegram): prevent subsequent final payloads from overwriting preview message

When multiple final payloads were dispatched (e.g., model text + tool error
warning), each one tried to edit the draft preview message, causing the last
payload (tool error) to replace the model's text. Guard the preview-edit path
with `!finalizedViaPreviewMessage` so only the first final payload edits the
preview; subsequent payloads are sent as separate messages via deliverReplies.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/telegram/bot-message-dispatch.test.ts

@@ -259,4 +259,44 @@ describe("dispatchTelegramMessage draft streaming", () => {
       }),
     );
   });
+
+  it("does not overwrite preview with subsequent final payloads", async () => {
+    const draftStream = createDraftStream(999);
+    createTelegramDraftStream.mockReturnValue(draftStream);
+    dispatchReplyWithBufferedBlockDispatcher.mockImplementation(
+      async ({ dispatcherOptions, replyOptions }) => {
+        await replyOptions?.onPartialReply?.({ text: "Checking..." });
+        // First final payload: model text → edits the preview.
+        await dispatcherOptions.deliver({ text: "Here are your results" }, { kind: "final" });
+        // Second final payload: tool error warning → should NOT overwrite the preview.
+        await dispatcherOptions.deliver(
+          { text: "⚠️ 🛠️ Exec: cmd failed: error" },
+          { kind: "final" },
+        );
+        return { queuedFinal: true };
+      },
+    );
+    deliverReplies.mockResolvedValue({ delivered: true });
+    editMessageTelegram.mockResolvedValue({ ok: true, chatId: "123", messageId: "999" });
+
+    await dispatchWithContext({ context: createContext() });
+
+    // Preview should be edited only once with the first final payload.
+    expect(editMessageTelegram).toHaveBeenCalledTimes(1);
+    expect(editMessageTelegram).toHaveBeenCalledWith(
+      123,
+      999,
+      "Here are your results",
+      expect.any(Object),
+    );
+    // Second final payload should fall through to deliverReplies as a new message.
+    expect(deliverReplies).toHaveBeenCalledTimes(1);
+    expect(deliverReplies).toHaveBeenCalledWith(
+      expect.objectContaining({
+        replies: [expect.objectContaining({ text: "⚠️ 🛠️ Exec: cmd failed: error" })],
+      }),
+    );
+    // Preview should NOT be cleared since it was finalized via edit.
+    expect(draftStream.clear).not.toHaveBeenCalled();
+  });
 });

src/telegram/bot-message-dispatch.ts

@@ -287,7 +287,12 @@ export const dispatchTelegramMessage = async ({
                 | undefined
             )?.buttons;
             let draftStoppedForPreviewEdit = false;
-            if (!hasMedia && payload.text && typeof previewMessageId === "number") {
+            if (
+              !finalizedViaPreviewMessage &&
+              !hasMedia &&
+              payload.text &&
+              typeof previewMessageId === "number"
+            ) {
               const canFinalizeViaPreviewEdit = payload.text.length <= draftMaxChars;
               if (canFinalizeViaPreviewEdit) {
                 draftStream?.stop();