Add Notification Backend Protocol (#24)

Reviewed-on: #24

src/va_agent/agent.py

@@ -1,5 +1,7 @@
 """ADK agent with vector search RAG tool."""
 
+from functools import partial
+
 from google import genai
 from google.adk.agents.llm_agent import Agent
 from google.adk.runners import Runner
@@ -10,8 +12,9 @@ from google.genai.types import Content, Part
 
 from va_agent.auth import auth_headers_provider
 from va_agent.config import settings
+from va_agent.dynamic_instruction import provide_dynamic_instruction
 from va_agent.governance import GovernancePlugin
-from va_agent.notifications import NotificationService
+from va_agent.notifications import FirestoreNotificationBackend
 from va_agent.session import FirestoreSessionService
 
 # MCP Toolset for RAG knowledge search
@@ -32,10 +35,11 @@ session_service = FirestoreSessionService(
 )
 
 # Notification service
-notification_service = NotificationService(
+notification_service = FirestoreNotificationBackend(
     db=firestore_db,
     collection_path=settings.notifications_collection_path,
     max_to_notify=settings.notifications_max_to_notify,
+    window_hours=settings.notifications_window_hours,
 )
 
 # Agent with static and dynamic instructions
@@ -43,11 +47,11 @@ governance = GovernancePlugin()
 agent = Agent(
     model=settings.agent_model,
     name=settings.agent_name,
+    instruction=partial(provide_dynamic_instruction, notification_service),
     static_instruction=Content(
         role="user",
         parts=[Part(text=settings.agent_instructions)],
     ),
-    instruction=settings.agent_instructions,
     tools=[toolset],
     after_model_callback=governance.after_model_callback,
 )