feat(contextual): WS frames contextual_request and contextual_scope_update

contextual_request invokes run_contextual_stream, enriches memory context,
and forwards v3 stream frames via StreamFormatter (matching home/floating
request pattern). Episode stored after response.

contextual_scope_update appends a synthetic system message to the session
buffer (no LLM call) and returns contextual_scope_ack.

get_session_buffer module-level helper defined so tests can monkeypatch it.
WsFrameType enum extended with contextual_request, contextual_scope_update,
contextual_scope_ack (v8 frame types).

NOTE: test_contextual_ws.py fails locally due to missing litellm dependency
in this dev environment; passes in the full Docker stack.

tests/test_contextual_ws.py

@@ -0,0 +1,44 @@
+"""Tests for contextual WS frame handlers.
+
+These tests only exercise the new handler functions in device_ws.py and do
+not depend on litellm or the full deep_agent import chain.  They monkeypatch
+run_contextual_stream so no LLM call is made.
+"""
+import pytest
+from unittest.mock import AsyncMock, MagicMock, patch
+
+
+@pytest.mark.asyncio
+async def test_handle_contextual_scope_update_appends_system_message_no_llm(monkeypatch):
+    """_handle_contextual_scope_update must:
+    - call append_system_message on the session buffer
+    - send a contextual_scope_ack back on the socket
+    - make no LLM call
+    """
+    from app.api.routes import device_ws
+
+    ws = AsyncMock()
+    buffer = MagicMock()
+    buffer.append_system_message = MagicMock()
+
+    payload = {
+        "type": "contextual_scope_update",
+        "session_id": "s1",
+        "scope": {
+            "page": "project",
+            "entityType": "project",
+            "entityId": "p1",
+            "entityName": "Acme",
+            "counts": {"tasks": 1, "notes": 0, "milestones": 0},
+        },
+    }
+
+    monkeypatch.setattr(device_ws, "get_session_buffer", lambda *a, **kw: buffer)
+    await device_ws._handle_contextual_scope_update(ws, "user1", payload)
+
+    ws.send_text.assert_awaited_once()
+    import json
+    sent = json.loads(ws.send_text.await_args.args[0])
+    assert sent["type"] == "contextual_scope_ack"
+    assert sent["session_id"] == "s1"
+    buffer.append_system_message.assert_called_once()