Enhance image handling in platform adapters

- Updated the image generation function description to clarify usage with markdown.
- Added `send_image` method to `BasePlatformAdapter` for native image sending across platforms.
- Implemented `send_image` in `DiscordAdapter` and `TelegramAdapter` to handle image attachments directly.
- Introduced `extract_images` method to extract image URLs from markdown and HTML, improving content processing.
- Enhanced message handling to support sending images as attachments while maintaining text content.

gateway/platforms/telegram.py

@@ -174,6 +174,31 @@ class TelegramAdapter(BasePlatformAdapter):
         except Exception as e:
             return SendResult(success=False, error=str(e))
     
+    async def send_image(
+        self,
+        chat_id: str,
+        image_url: str,
+        caption: Optional[str] = None,
+        reply_to: Optional[str] = None,
+    ) -> SendResult:
+        """Send an image natively as a Telegram photo."""
+        if not self._bot:
+            return SendResult(success=False, error="Not connected")
+        
+        try:
+            # Telegram can send photos directly from URLs
+            msg = await self._bot.send_photo(
+                chat_id=int(chat_id),
+                photo=image_url,
+                caption=caption[:1024] if caption else None,  # Telegram caption limit
+                reply_to_message_id=int(reply_to) if reply_to else None,
+            )
+            return SendResult(success=True, message_id=str(msg.message_id))
+        except Exception as e:
+            print(f"[{self.name}] Failed to send photo, falling back to URL: {e}")
+            # Fallback: send as text link
+            return await super().send_image(chat_id, image_url, caption, reply_to)
+    
     async def send_typing(self, chat_id: str) -> None:
         """Send typing indicator."""
         if self._bot: