[Misc][Doc] Add the latest stable release url (vllm-project#826)

### What this PR does / why we need it?
 Add the latest stable release url

Signed-off-by: hfadzxy <starmoon_zhang@163.com>

Author: hfadzxy

docs/source/_templates/sections/header.html

@@ -0,0 +1,58 @@
+<!--
+  **********************************************************************
+  * Copyright (c) 2025 Huawei Technologies Co., Ltd. All Rights Reserved.
+  * Copyright 2023 The vLLM team.
+  *
+  * 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.
+  * This file is a part of the vllm-ascend project.
+  * Adapted from https://github.com/vllm-project/vllm/blob/main/docs/source/_templates/sections/header.html
+  **********************************************************************
+-->
+<style>
+    .notification-bar {
+      width: 100vw;
+      display: flex;
+      justify-content: center;
+      align-items: center;
+      font-size: 16px;
+    }
+    .notification-bar p {
+      margin: 0;
+    }
+    .notification-bar a {
+      font-weight: bold;
+      text-decoration: none;
+    }
+  
+    /* Light mode styles (default) */
+    .notification-bar {
+      background-color: #fff3cd;
+      color: #856404;
+    }
+    .notification-bar a {
+      color: #d97706;
+    }
+  
+    /* Dark mode styles */
+    html[data-theme=dark] .notification-bar {
+      background-color: #333;
+      color: #ddd;
+    }
+    html[data-theme=dark] .notification-bar a {
+      color: #ffa500; /* Brighter color for visibility */
+    }
+  </style>
+  
+  <div class="notification-bar">
+    <p>You are viewing the latest developer preview docs. <a href="https://vllm-ascend.readthedocs.io/en/stable/">Click here</a> to view docs for the latest stable release(v0.7.3).</p>
+  </div>

docs/source/conf.py

@@ -23,7 +23,8 @@
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #
-# import os
+import os
+
 # import sys
 # sys.path.insert(0, os.path.abspath('.'))
 
@@ -119,6 +120,16 @@
 # so a file named "default.css" will overwrite the builtin "default.css".
 # html_static_path = ['_static']
 
+READTHEDOCS_VERSION_TYPE = os.environ.get('READTHEDOCS_VERSION_TYPE')
+if READTHEDOCS_VERSION_TYPE == "tag":
+    # remove the warning banner if the version is a tagged release
+    header_file = os.path.join(os.path.dirname(__file__),
+                               "_templates/sections/header.html")
+    # The file might be removed already if the build is triggered multiple times
+    # (readthedocs build both HTML and PDF versions separately)
+    if os.path.exists(header_file):
+        os.remove(header_file)
+
 
 def setup(app):
     pass