feat(telegram): add document file processing for PDF, text, and Office files

Download, cache, and enrich document files sent via Telegram. Supports
.pdf, .md, .txt, .docx, .xlsx, .pptx with size validation, unsupported
type rejection, text content injection for .md/.txt, and hourly cache
cleanup.

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

gateway/platforms/telegram.py

@@ -8,6 +8,7 @@ Uses python-telegram-bot library for:
 """
 
 import asyncio
+import os
 import re
 from typing import Dict, List, Optional, Any
 
@@ -42,6 +43,8 @@ from gateway.platforms.base import (
     SendResult,
     cache_image_from_bytes,
     cache_audio_from_bytes,
+    cache_document_from_bytes,
+    SUPPORTED_DOCUMENT_TYPES,
 )
 
 
@@ -419,6 +422,8 @@ class TelegramAdapter(BasePlatformAdapter):
             msg_type = MessageType.AUDIO
         elif msg.voice:
             msg_type = MessageType.VOICE
+        elif msg.document:
+            msg_type = MessageType.DOCUMENT
         else:
             msg_type = MessageType.DOCUMENT
         
@@ -479,7 +484,70 @@ class TelegramAdapter(BasePlatformAdapter):
                 print(f"[Telegram] Cached user audio: {cached_path}", flush=True)
             except Exception as e:
                 print(f"[Telegram] Failed to cache audio: {e}", flush=True)
-        
+
+        # Download document files to cache for agent processing
+        elif msg.document:
+            doc = msg.document
+            try:
+                # Determine file extension
+                ext = ""
+                original_filename = doc.file_name or ""
+                if original_filename:
+                    _, ext = os.path.splitext(original_filename)
+                    ext = ext.lower()
+
+                # If no extension from filename, reverse-lookup from MIME type
+                if not ext and doc.mime_type:
+                    mime_to_ext = {v: k for k, v in SUPPORTED_DOCUMENT_TYPES.items()}
+                    ext = mime_to_ext.get(doc.mime_type, "")
+
+                # Check if supported
+                if ext not in SUPPORTED_DOCUMENT_TYPES:
+                    supported_list = ", ".join(sorted(SUPPORTED_DOCUMENT_TYPES.keys()))
+                    event.text = (
+                        f"Unsupported document type '{ext or 'unknown'}'. "
+                        f"Supported types: {supported_list}"
+                    )
+                    print(f"[Telegram] Unsupported document type: {ext or 'unknown'}", flush=True)
+                    await self.handle_message(event)
+                    return
+
+                # Check file size (Telegram Bot API limit: 20 MB)
+                if doc.file_size and doc.file_size > 20 * 1024 * 1024:
+                    event.text = (
+                        "The document is too large (over 20 MB). "
+                        "Please send a smaller file."
+                    )
+                    print(f"[Telegram] Document too large: {doc.file_size} bytes", flush=True)
+                    await self.handle_message(event)
+                    return
+
+                # Download and cache
+                file_obj = await doc.get_file()
+                doc_bytes = await file_obj.download_as_bytearray()
+                raw_bytes = bytes(doc_bytes)
+                cached_path = cache_document_from_bytes(raw_bytes, original_filename or f"document{ext}")
+                mime_type = SUPPORTED_DOCUMENT_TYPES[ext]
+                event.media_urls = [cached_path]
+                event.media_types = [mime_type]
+                print(f"[Telegram] Cached user document: {cached_path}", flush=True)
+
+                # For text files, inject content into event.text
+                if ext in (".md", ".txt"):
+                    try:
+                        text_content = raw_bytes.decode("utf-8")
+                        display_name = original_filename or f"document{ext}"
+                        injection = f"[Content of {display_name}]:\n{text_content}"
+                        if event.text:
+                            event.text = f"{injection}\n\n{event.text}"
+                        else:
+                            event.text = injection
+                    except UnicodeDecodeError:
+                        print(f"[Telegram] Could not decode text file as UTF-8, skipping content injection", flush=True)
+
+            except Exception as e:
+                print(f"[Telegram] Failed to cache document: {e}", flush=True)
+
         await self.handle_message(event)
     
     async def _handle_sticker(self, msg: Message, event: "MessageEvent") -> None: