feat(max-bot): implement mock-based message flow with WIP file queue

- MAX API integration (long polling)
- MockPlatformClient for agent simulation
- File download & workspace storage
- Basic commands: /help, /start
- Attachment queue: add works, list/remove need testing

[WIP: attachment queue commands]
[MOCK-ONLY: requires real agent for production]

adapter/max/bot.py

@@ -33,13 +33,20 @@ from core.auth import AuthManager
 from core.chat import ChatManager
 from core.handler import EventDispatcher
 from core.handlers import register_all
-from core.protocol import Attachment, IncomingCommand, OutgoingEvent, OutgoingMessage
-from core.protocol import OutgoingNotification, OutgoingTyping, OutgoingUI
+from core.protocol import (
+    Attachment,
+    IncomingCommand,
+    IncomingMessage,
+    OutgoingEvent,
+    OutgoingMessage,
+    OutgoingNotification, 
+    OutgoingTyping, 
+    OutgoingUI
+)
 from core.settings import SettingsManager
 from core.store import InMemoryStore, StateStore
 from sdk.interface import PlatformClient, PlatformError
 from sdk.prototype_state import PrototypeStateStore
-from sdk.real import RealPlatformClient
 
 logger = structlog.get_logger(__name__)
 
@@ -130,6 +137,7 @@ class MaxBotApp:
             self.registry: AgentRegistry = load_from_env()
         except (AgentRegistryError, OSError) as exc:
             raise RuntimeError("failed to load MAX agent registry") from exc
+        
 
         self.chat_store = ChatStore()
         self.max_chat_handler = MaxChatHandler(self.chat_store)
@@ -138,22 +146,35 @@ class MaxBotApp:
         self.core_store: StateStore = InMemoryStore()
         self.prototype_state = PrototypeStateStore()
 
-        delegates: dict[str, RealPlatformClient] = {}
-        for agent in self.registry.agents:
-            base_raw = agent.base_url.strip() if agent.base_url else agent_base_url
-            delegates[agent.agent_id] = RealPlatformClient(
-                agent_id=agent.agent_id,
-                agent_base_url=base_raw,
-                prototype_state=self.prototype_state,
-                platform="max",
-            )
+        backend_mode = os.environ.get("MAX_PLATFORM_BACKEND", "mock").strip().lower()
+        logger.info("max_platform_backend_selected", backend=backend_mode)
 
-        default_client = next(iter(delegates.values()))
-        self.platform: RoutedMaxPlatformClient = RoutedMaxPlatformClient(
-            chat_store=self.chat_store,
-            delegates=delegates,
-            default_client=default_client,
-        )
+        if backend_mode == "real":
+            from sdk.real import RealPlatformClient
+            delegates: dict[str, RealPlatformClient] = {}
+            for agent in self.registry.agents:
+                base_raw = agent.base_url.strip() if agent.base_url else agent_base_url
+                delegates[agent.agent_id] = RealPlatformClient(
+                    agent_id=agent.agent_id,
+                    agent_base_url=base_raw,
+                    prototype_state=self.prototype_state,
+                    platform="max",
+                )
+            
+            if not delegates:
+                raise RuntimeError("No agents configured for real backend")
+            
+            default_client = next(iter(delegates.values()))
+            self.platform: RoutedMaxPlatformClient = RoutedMaxPlatformClient(
+                chat_store=self.chat_store,
+                delegates=delegates,
+                default_client=default_client,
+            )
+        else:
+            # Mock backend for local development/testing
+            logger.warning("max_using_mock_backend", note="No real agent connection")
+            from sdk.mock import MockPlatformClient
+            self.platform = MockPlatformClient()  # type: ignore[assignment]
 
         self.chat_mgr = ChatManager(self.platform, self.core_store)
         self.auth_mgr = AuthManager(self.platform, self.core_store)
@@ -244,6 +265,10 @@ class MaxBotApp:
         return refreshed
 
     async def process_message_created(self, payload: dict) -> None:
+        logger.info(
+            "DEBUG_PAYLOAD",
+            body=payload.get("message", {}).get("body"),
+        )
         message = payload.get("message")
         if not isinstance(message, dict):
             return
@@ -289,7 +314,9 @@ class MaxBotApp:
         attachments_core = await self._materialize_attachments(room, attachments_core, raw_meta)
 
         if attachments_core and not text:
+            logger.info("QUEUE_ADD", chat_key=chat_key, count=len(attachments_core))
             for att in attachments_core:
+                logger.info("QUEUE_ITEM", filename=att.filename)
                 self.chat_store.stage_attachment(chat_key, (att.workspace_path or "", att.filename or "file"))
             return
 
@@ -345,6 +372,7 @@ class MaxBotApp:
 
     async def _handle_local_attachment_command(self, incoming: IncomingCommand, chat_key: str) -> str:
         if incoming.command == "list":
+            logger.info("QUEUE_LIST_REQUEST", chat_key=chat_key) 
             return self.attach_handler.handle_list(chat_key)
         return self.attach_handler.handle_remove(chat_key, incoming.args[0] if incoming.args else "")
 
@@ -463,7 +491,7 @@ class MaxBotApp:
             deeplink_note = f" (payload: {dl})"
 
         welcome = (
-            "Здравствуйте, я помогу с задачами Lambda. "
+            "Здравствуйте, я бот Lambda, который готов помочь с задачами."
             f"Отправьте текст или файл.{deeplink_note}"
         )