feat(sdk): add host integration extension points

nanobot/sdk/clients.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from collections.abc import Iterable, Mapping
+from collections.abc import Callable, Iterable, Mapping
 from copy import deepcopy
 from pathlib import Path
 from typing import TYPE_CHECKING, Any
@@ -18,6 +18,8 @@ from nanobot.session.manager import replay_max_messages_for_context
 
 if TYPE_CHECKING:
     from nanobot.agent.loop import AgentLoop
+    from nanobot.bus.runtime_events import RuntimeEventHandler, RuntimeEventType
+    from nanobot.runtime_context import RuntimeContextProvider
 
 
 class SessionClient:
@@ -193,6 +195,21 @@ class RuntimeClient:
         """Current runtime workspace."""
         return self._loop.workspace
 
+    def add_context_provider(
+        self,
+        provider: RuntimeContextProvider,
+    ) -> Callable[[], None]:
+        """Register per-turn model context and return an unsubscribe callback."""
+        return self._loop.register_runtime_context_provider(provider)
+
+    def subscribe(
+        self,
+        event_type: RuntimeEventType,
+        handler: RuntimeEventHandler,
+    ) -> Callable[[], None]:
+        """Subscribe to one runtime event type and return an unsubscribe callback."""
+        return self._loop.runtime_events.subscribe(handler, event_type)
+
     async def compact_session(self, session_key: str) -> SessionSnapshot:
         """Run token/replay-window consolidation for one session."""
         session = self._loop.sessions.get_or_create(session_key)