Tests: fix failling http in CI (#13301)

### What problem does this PR solve?
test_doc_sdk_routes_unit had two flaky/incorrect branch assumptions:

1. parse/stop_parsing production logic gates on doc.run, but tests used
progress, causing branch mismatch and unintended fallthrough into
mutation/DB paths.
2. stop_parsing invalid-state test asserted an outdated message
fragment, making the contract brittle.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

api/apps/sdk/doc.py

@@ -809,6 +809,10 @@ async def delete(tenant_id, dataset_id):
     return get_result()
 
 
+DOC_STOP_PARSING_INVALID_STATE_MESSAGE = "Can't stop parsing document that has not started or already completed"
+DOC_STOP_PARSING_INVALID_STATE_ERROR_CODE = "DOC_STOP_PARSING_INVALID_STATE"
+
+
 @manager.route("/datasets/<dataset_id>/chunks", methods=["POST"])  # noqa: F821
 @token_required
 async def parse(tenant_id, dataset_id):
@@ -947,7 +951,11 @@ async def stop_parsing(tenant_id, dataset_id):
         if not doc:
             return get_error_data_result(message=f"You don't own the document {id}.")
         if doc[0].run != TaskStatus.RUNNING.value :
-            return get_error_data_result("Can't stop parsing document that has not started or already completed")
+            return construct_json_result(
+                code=RetCode.DATA_ERROR,
+                message=DOC_STOP_PARSING_INVALID_STATE_MESSAGE,
+                data={"error_code": DOC_STOP_PARSING_INVALID_STATE_ERROR_CODE},
+            )
         # Send cancellation signal via Redis to stop background task
         cancel_all_task_of(id)
         info = {"run": "2", "progress": 0, "chunk_num": 0}