refactor: replace orchestrator with LangGraph deep-agent supervisors

- Add app/core/deep_agent.py with Home and Floating supervisor graphs
  using LangGraph create_react_agent (hierarchical pattern)
- Strip ChatAgent classes from all 4 agent files, keep @tool functions
- Rewrite output_formatter.py for event-based (token/tool_end/mutations) stream
- Update device_ws.py to use run_home_stream/run_floating_stream
- Rewrite chat.py REST route to use run_home
- Add update_core_memory tool to both supervisors
- Add langgraph>=0.3.0 to requirements.txt
- Remove orchestrator.py, execution_plan.py, agent_registry.py, plans.py
- Remove PlanAction, PlanStep, ExecutionPlan, execution_mode from schemas
- Update all affected tests to match new API
- Remove 6 deprecated test files for deleted modules
- Clean up stale docstrings referencing removed orchestrator

tests/test_middleware.py

@@ -20,7 +20,6 @@ from jose import jwt
 from app.config.settings import settings
 from app.db import get_session
 from app.main import app
-from app.schemas import ChatResponse
 from tests.conftest import TEST_USER_IDS
 
 # ---------------------------------------------------------------------------
@@ -50,7 +49,6 @@ _CHAT_BODY = {
         "recent_tasks": [],
         "conversation_history": [],
     },
-    "execution_mode": "direct",
 }
 
 
@@ -240,7 +238,7 @@ class TestRateLimitMiddleware:
 
 
 class TestSanitizerMiddleware:
-    """Mock ``orchestrate`` to inject controlled strings into chat responses."""
+    """Mock ``run_home`` to inject controlled strings into chat responses."""
 
     _CHAT_PATH = "/api/v1/chat"
 
@@ -248,11 +246,10 @@ class TestSanitizerMiddleware:
         return _make_jwt(user_id=str(uuid.uuid4()), tier="pro")
 
     def _post_chat(self, client: TestClient, response_text: str) -> dict:
-        mock_response = ChatResponse(response=response_text, actions=[])
         with patch(
-            "app.api.routes.chat.orchestrate",
+            "app.api.routes.chat.run_home",
             new_callable=AsyncMock,
-            return_value=mock_response,
+            return_value=response_text,
         ):
             resp = client.post(
                 self._CHAT_PATH,