fix: strip MarkdownV2 escapes from Telegram plaintext fallback

When Telegram's MarkdownV2 parser rejects a message, the send() fallback
was sending the already-escaped text as plain text. This caused users to
see raw backslashes before every special character (periods, dashes,
parentheses, etc.) — e.g. 'sentence\.' or '\-\-auto\-approve'.

Changes:
- Add _strip_mdv2() to reverse MarkdownV2 escaping for clean plaintext
- Use stripped text in the send() fallback path instead of raw escaped chunk
- Add logging when the MDV2 fallback is triggered for diagnostics
- Add logger to telegram.py (was missing)

The edit_message() fallback already correctly used the original content;
this brings send() in line with that behavior.

gateway/platforms/telegram.py

@@ -8,10 +8,13 @@ Uses python-telegram-bot library for:
 """
 
 import asyncio
+import logging
 import os
 import re
 from typing import Dict, List, Optional, Any
 
+logger = logging.getLogger(__name__)
+
 try:
     from telegram import Update, Bot, Message
     from telegram.ext import (
@@ -73,6 +76,19 @@ def _escape_mdv2(text: str) -> str:
     return _MDV2_ESCAPE_RE.sub(r'\\\1', text)
 
 
+def _strip_mdv2(text: str) -> str:
+    """Strip MarkdownV2 escape backslashes to produce clean plain text.
+
+    Also removes MarkdownV2 bold markers (*text* -> text) so the fallback
+    doesn't show stray asterisks from header/bold conversion.
+    """
+    # Remove escape backslashes before special characters
+    cleaned = re.sub(r'\\([_*\[\]()~`>#\+\-=|{}.!\\])', r'\1', text)
+    # Remove MarkdownV2 bold markers that format_message converted from **bold**
+    cleaned = re.sub(r'\*([^*]+)\*', r'\1', cleaned)
+    return cleaned
+
+
 class TelegramAdapter(BasePlatformAdapter):
     """
     Telegram bot adapter.
@@ -199,9 +215,13 @@ class TelegramAdapter(BasePlatformAdapter):
                 except Exception as md_error:
                     # Markdown parsing failed, try plain text
                     if "parse" in str(md_error).lower() or "markdown" in str(md_error).lower():
+                        logger.warning("[%s] MarkdownV2 parse failed, falling back to plain text: %s", self.name, md_error)
+                        # Strip MDV2 escape backslashes so the user doesn't
+                        # see raw backslashes littered through the message.
+                        plain_chunk = _strip_mdv2(chunk)
                         msg = await self._bot.send_message(
                             chat_id=int(chat_id),
-                            text=chunk,
+                            text=plain_chunk,
                             parse_mode=None,  # Plain text
                             reply_to_message_id=int(reply_to) if reply_to and i == 0 else None,
                             message_thread_id=int(thread_id) if thread_id else None,