更新文档，调整内存 URI 格式和写入模式示例；移除过时的 OpenViking 内容补充逻辑，并添加相应的单元测试

skills/memory-system-api/references/api.md

@@ -197,13 +197,15 @@ curl -sS -X POST "<MEMORY_SYSTEM_BASE_URL>/memory-system/memories" \
   -d '{
     "user_id": "<USER_ID>",
     "user_key": "<USER_KEY>",
-    "uri": "viking://user/memories/preferences/python.md",
-    "content": "# Python 偏好\n\n用户偏好使用 Python 做数据分析，常用 pandas。",
-    "mode": "replace",
+    "uri": "viking://user/<USER_ID>/memories/preferences/饮食偏好.md",
+    "content": "用户喜欢喝茶",
+    "mode": "create",
     "wait": true
   }'
 ```
 
+For preference memories, write directly under `memories/preferences/`; do not add an extra `/user` path segment.
+
 `mode` supports:
 
 - `create`: create a new memory URI.
@@ -262,7 +264,7 @@ curl -s -X POST <MEMORY_SYSTEM_BASE_URL>/memory-system/search \
   }'
 ```
 
-Raw API search responses include merged `items` plus compact backend diagnostics. Fields named `vector` are stripped recursively before the API returns JSON. The API does not return EverOS `original_data` or full episode payloads inside `backends` anymore. OpenViking search uses `/api/v1/search/search`; `target_uri`, `level`, and `score_threshold` are optional request fields. For OpenViking memory hits, the API also reads the matched URI with `content/read` and returns the latest body in `content` when available.
+Raw API search responses include merged `items` plus compact backend diagnostics. Fields named `vector` are stripped recursively before the API returns JSON. The API does not return EverOS `original_data` or full episode payloads inside `backends` anymore. OpenViking search uses `/api/v1/search/search`; `target_uri`, `level`, and `score_threshold` are optional request fields.
 
 The search response shape should now look more like: