Refactor: migrate chunk retrieval_test and knowledge_graph to REST API endpoints (#14402)

### What problem does this PR solve?

## Summary

Migrate two web API endpoints to REST-style HTTP API endpoints,
following the pattern established in #14222:

| Old Endpoint | New Endpoint |
|---|---|
| `POST /v1/chunk/retrieval_test` | `POST
/api/v1/datasets/<dataset_id>/search` |
| `GET /v1/chunk/knowledge_graph` | `GET
/api/v1/datasets/<dataset_id>/graph` |

test/testcases/test_http_api/common.py

@@ -517,3 +517,12 @@ def get_flattened_metadata(auth, dataset_ids, *, headers=HEADERS):
     url = f"{HOST_ADDRESS}{DATASETS_API_URL}/metadata/flattened"
     res = requests.get(url=url, headers=headers, auth=auth, params={"dataset_ids": ",".join(dataset_ids)})
     return res.json()
+
+
+def search_dataset(auth, dataset_id, payload=None, *, headers=HEADERS):
+    url = f"{HOST_ADDRESS}{DATASETS_API_URL}/{dataset_id}/search"
+    res = requests.post(url=url, headers=headers, auth=auth, json=payload)
+    return res.json()
+
+
+

test/testcases/test_http_api/test_dataset_management/test_search.py

@@ -0,0 +1,83 @@
+#
+#  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+import pytest
+from common import search_dataset, knowledge_graph
+from configs import INVALID_API_TOKEN
+from libs.auth import RAGFlowHttpApiAuth
+
+
+@pytest.mark.p2
+class TestAuthorization:
+    @pytest.mark.parametrize(
+        "invalid_auth, expected_code, expected_message",
+        [
+            (None, 401, "<Unauthorized '401: Unauthorized'>"),
+            (RAGFlowHttpApiAuth(INVALID_API_TOKEN), 401, "<Unauthorized '401: Unauthorized'>"),
+        ],
+    )
+    def test_invalid_auth(self, invalid_auth, expected_code, expected_message):
+        res = search_dataset(invalid_auth, "dataset_id", {"question": "test"})
+        assert res["code"] == expected_code
+        assert expected_message in res.get("message", "")
+
+
+class TestDatasetSearch:
+    @pytest.mark.p2
+    def test_search_without_question(self, HttpApiAuth, add_dataset_func):
+        dataset_id = add_dataset_func
+        res = search_dataset(HttpApiAuth, dataset_id, {})
+        assert res["code"] == 101, res
+
+    @pytest.mark.p2
+    def test_search_basic(self, HttpApiAuth, add_chunks):
+        dataset_id, document_id, _ = add_chunks
+        res = search_dataset(HttpApiAuth, dataset_id, {"question": "chunk"})
+        assert res["code"] == 0, res
+        assert "chunks" in res["data"], res
+
+    @pytest.mark.p2
+    def test_search_with_doc_ids(self, HttpApiAuth, add_chunks):
+        dataset_id, document_id, _ = add_chunks
+        res = search_dataset(HttpApiAuth, dataset_id, {"question": "chunk", "doc_ids": [document_id]})
+        assert res["code"] == 0, res
+        assert "chunks" in res["data"], res
+
+    @pytest.mark.p2
+    @pytest.mark.parametrize(
+        "payload, expected_code",
+        [
+            ({"question": "chunk", "page": 1, "size": 2}, 0),
+            ({"question": "chunk", "similarity_threshold": 0.5}, 0),
+            ({"question": "chunk", "vector_similarity_weight": 0.7}, 0),
+            ({"question": "chunk", "top_k": 10}, 0),
+        ],
+    )
+    def test_search_params(self, HttpApiAuth, add_chunks, payload, expected_code):
+        dataset_id, _, _ = add_chunks
+        res = search_dataset(HttpApiAuth, dataset_id, payload)
+        assert res["code"] == expected_code, res
+
+
+@pytest.mark.p2
+class TestDatasetGraph:
+    def test_graph_requires_auth(self):
+        res = knowledge_graph(None, "dataset_id")
+        assert res["code"] == 401
+
+    def test_graph_basic(self, HttpApiAuth, add_dataset_func):
+        dataset_id = add_dataset_func
+        res = knowledge_graph(HttpApiAuth, dataset_id)
+        assert res["code"] == 0, res