feat: preserve planner context across task steps

apps/device-host-agent/tests/test_cloud_planner_client.py

@@ -96,6 +96,36 @@ def test_decide_base64_encodes_screenshot() -> None:
     assert body["screenshot_base64"] == "aGVsbG8="
 
 
+def test_decide_forwards_planner_history() -> None:
+    seen_requests: list[httpx.Request] = []
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        seen_requests.append(request)
+        return httpx.Response(200, json={"tool_name": "tap", "arguments": {}})
+
+    client = _client(handler)
+    history = [
+        {
+            "user_prompt": "first screen",
+            "tool_name": "tap",
+            "arguments": {"x": 1, "y": 2},
+            "rationale": "Open it.",
+            "tool_result": {"success": True},
+        }
+    ]
+
+    client.decide(
+        system_prompt="sp",
+        user_prompt="next screen",
+        screenshot=None,
+        tools=_TOOLS,
+        timeout=10.0,
+        history=history,
+    )
+
+    assert json.loads(seen_requests[0].content)["history"] == history
+
+
 def test_decide_clamps_legacy_timeout_and_waits_for_cloud_profile_timeout() -> None:
     seen_requests: list[httpx.Request] = []